Leonard Hofstadter is an experimental physicist at Caltech in Pasadena. Although Leonard has many geeky interests and hobbies, he was the most willing of the guys to try and socialize with other people. Leonard's interest in Penny brought her into the guys social group and helped bring Leonard, and indeed all of the guys, out of their shells. Leonard and Penny were married 2015 and, after a year of splitting time between apartments 4A and 4B, now live alone in 4A.
Leonard is known for his black-framed glasses and earth-toned jackets and hoodies. He usually wears these over superhero, physics, or environmental t-shirts, and his shoes typically consist of low-cut black Converse All Star sneakers. As a child, he seems to have had a rough time socially. He was bullied in school, having been beaten up or stuffed into his cello case. Family life was not much better as Leonard felt unloved and under appreciated by his parents. Leonard's family did not celebrate birthdays or Christmas, something Leonard felt bad about. Due to the lack of affection from his mother, Leonard developed a hugging machine.
Leonard is from a high-achieving family and has often felt overlooked by his parents, who concentrated on his siblings. All the members of his family are quite accomplished in their fields.
Leonard's mother, Dr. Beverly Hofstadter, is a psychiatrist and neuroscientist. At best, her mothering style would be described as cold and distant. She did not heap love or praise on Leonard as a child. She has developed a friendly relationship with Sheldon that is closer than her relationship with Leonard. When Leonard decided to write a novel, he was concerned that the lead character, a “confident, ballbusting” woman who is blond and mean, was unconsciously based on Penny. After Leonard chatted with his mother, he realized the character was actually based on Beverly. Looking at the sexual tension in his story in a new light, Leonard abandoned the novel.
Leonard's father, Dr. Alfred Hofstadter is an anthropologist who worked with the Leaky family, leading to Leonard’s middle name. Leonard's relationship with him was distant as his father spent a lot of time away from home, working in the field. He and Leonard's mother do not get along, and he seems to have been cowed by Leonard's mother while they were married. From Leonard's comments, his father's physical health has improved since his divorce from Beverly.
Leonard has two siblings: his brother Michael, who is a tenured law professor at Harvard and was engaged to the youngest appellate court judge on the East coast; and an unnamed sister who is working on curing diabetes with her research at the point of being able to grow a human pancreas in a teenage gibbon.
Relationship with Penny
Leonard's infatuation with Penny began the day he saw her moving into the apartment across the hall. Despite Sheldon's disinclination to socialize with their new neighbor, Leonard invited her over for lunch. After a year of living across the hall from each other, Leonard finally asked Penny out and she accepted. After an "okay" date, Penny broke things off as she feared she wasn't smart enough to date a guy like Leonard. The pair went back to dating other people.
After Sheldon was offered the chance to lead a three month research expedition in the Arctic, he invited Leonard, Howard and Raj to go along and help him. When Penny found out Leonard would be away for months, her feelings for him became clearer. Although she couldn't build up the courage to tell Leonard not to go, she was able to voice her sadness after he left.
When Leonard returned from the three-month trip, Penny kissed him and, though there were a couple of days of uncertainty, they started a relationship. After nine months, Leonard and Penny's relationship came to an end when Leonard told Penny he loved her and she couldn't say the same back. Despite the awkwardness, the pair vowed to work at remaining friends, even as they began to date other people.
Penny was initially supportive when Leonard started dating Raj's sister, Priya. But later his and Penny's friendship suffered when Priya demanded that he stay away from Penny. When Leonard and Priya's relationship ended a few months after her return to India, Penny and Leonard resumed their friendship, even going out together as friends.
One day, Leonard viewed Penny through her open door wearing the same top she had worn the first time he saw her. As a result, he spontaneously asked Penny out on a date, which she accepted. Wanting to try and make the relationship work, they decided on a “beta test”, working through any problems they saw in their relationship. Following this, Leonard and Penny got back together and have remained a couple since.
Although there were several months of awkwardness after Leonard proposed during sex, they spent the next year working on their relationship. They were able to correct problems they had the first time they were together. One of the major problems was Penny's inability to tell Leonard she loved him. When Penny worked on a project with a guy from school, it upset Leonard and made him jealous. Penny became angry when she and Leonard argued about his jealousy, and she accidentally blurted out that he's the one she loves - the first time she was able to say she loved him. After Penny confirmed that she loved him, she ran off to work before she and Leonard started crying.
They spent the next few months growing closer and more comfortable with each other, often eating together alone in Penny's apartment. When Leonard got an offer to work with Stephen Hawking's team for four months in the North Sea, Penny did not wish he was not going, as she did when he went to the Arctic. She fully supported him, worried about his having everything he needed, and though she knew she would miss him, she was sure their relationship was on a solid footing. After returning early to spend time with Penny alone, their relationship entered a quiet period until Penny got a part on a television show. After her part was cut, Penny became angry and depressed, drinking heavily.
When Leonard tried to cheer her up, a drunk and depressed Penny proposed to Leonard. Leonard, knowing Penny’s mental state, hesitated to answer. This angered Penny, who walked out and left him alone. Leonard feared their relationship was over, but Penny later assured him that he made the right decision. Penny, wanting to put her full effort into acting, quit the Cheesecake Factory to pursue acting full-time. Leonard was dubious about her change in job, and was hesitant about fully supporting her. Although hesitant about her career change, Leonard showed he was fully behind her when her car broke down. Penny didn't have the money to get it fixed, so Leonard bought her a car.
After getting fired from a bad, low-budget movie, Penny vowed to start making better life choices. When Leonard inquired as to what kind of choices, she told Leonard they should get married. At first, Leonard thought this was a repeat of her last proposal with Penny only wanting to get married because of her career problems, but she told him she now realized what was important to her. She convinced Leonard that his making her happy was the most important thing to her. After this, he got down on one knee and proposed to Penny, handing her an engagement ring he'd been carrying around for a couple of years.
Following their engagement, they had some discussions about money and whether they were doing the right thing. Leonard and Penny also considered living together, but Sheldon's dependence on Leonard made their moving out difficult. Sheldon agreed to let Leonard stay with Penny one night a week, while Penny stays in 4A with Leonard the rest of the time. After almost a year of no planning or even a discussion of a date, Sheldon pushed Leonard and Penny to set a wedding date. As a result, they started to consider what kind of wedding they wanted, even though neither one of them was in a hurry.
After Leonard said it doesn't matter whether they get married in a day or in fifty years, Penny told Leonard she was free that night and that Vegas isn't that far away. After Leonard agreed, the couple left to drive to Vegas. On the way, Leonard confessed to Penny that during his North Sea expedition he kissed another woman. Penny told Leonard she wasn't happy about the kiss, but she could get past it, so they carried on driving to Vegas.
In Vegas, they chose their wedding package and decided to have it streamed over the Internet so their friends could see it. Leonard prepared his own vows, while Penny quoted "You’ve Got a Friend in Me" from Toy Story, bringing Leonard to tears. After the wedding, in their hotel, Penny struggled with the kiss, asking Leonard if he felt guilty. He admitted he felt guilty every time he saw the woman at work. Knowing he still worked with the woman angered Penny, so they left Vegas, spending their wedding night in separate apartments back in Pasadena.
Sheldon suggested that if Penny talked to Mandy, the woman he kissed, it may ease her concern. When Leonard talked to the woman, she suggested that Leonard might be trying to sabotage the marriage. When Penny and Leonard discussed this , Penny admitted she may have been sabotaging the wedding in her own way with her reaction to Leonard's admission. As they talked, they realized they both felt they didn’t deserve the other, and were worried that the other would leave for something better. Leonard suggested that they stopped being scared of losing each other, and just be together.
When they tried to move out again a year later, Sheldon had a minor breakdown, causing them to maintain the status quo and continue to split their time between apartments 4A and 4B. After Bernadette became pregnant, Leonard and Penny talked about having a baby, but decided that it would be in the future as they didn't think they currently were ready for it. Knowing Penny's shopping habits and large amount of debt, Leonard had been keeping a bank account secret from Penny. After Penny found out, she admitted that she was keeping a secret from him, that she wasn't happy with her job.
After Penny found out Leonard's mother was still upset about not being invited to the wedding, she offered to have another small wedding ceremony while Beverly was still in town. As a result, Leonard was able to invite his father, and Penny invited her own family. It also allowed their friends to attend the ceremony instead of watching over the Internet. Those attending were Penny's father (Wyatt), mother (Susan), and Penny's brother (Randall), Leonard's father (Alfred) and mother (Beverly), Sheldon's mother (Mary), along with their friends Sheldon, Howard, Raj, Amy and Stuart, with Bernadette officiating.
After Amy's apartment suffered water damage, she and Sheldon agreed to move into Penny's apartment, while Leonard and Penny stayed alone in Sheldon and Leonard's apartment. After a few weeks, Penny started hiding Leonard's collectibles, while trying to add her own touches to the apartment. Finding out about this, Leonard suggested Penny redecorate the bedroom, while Leonard moved some of his things in Sheldon's old room. After her apartment's repair work was completed, Sheldon and Amy decided to continue living in Apartment 4B, allowing Leonard and Penny to stay by themselves in 4A.
When Penny invited her brother to stay with her and Leonard without telling Leonard. he objected and Penny ended up telling her father it was Leonard's fault her brother couldn't come. After Raj ran into financial trouble, Leonard and Penny offered him Sheldon's old room. This made Leonard uncomfortable when Penny and Raj bonded over clothes, shopping, wine, spa treatments, all the while ignoring Leonard. Beverly pointed out they may have a problem as they can't seem to live together by themselves. Leonard demonstrated some jealousy when Penny was tentatively offered a job with her old boyfriend, Zack. The worry turned out to be moot when she wasn't officially offered the job, because Zack's fiancé objected to him working with his old girlfriend.
After Sheldon and Amy got engaged and Howard and Bernadette revealed they were expecting another baby, Leonard threw a little party for Penny with decorations and a cake so she wouldn't feel left out by the developments in their friends' lives. Penny said that compared to Bernadette, who has to grow a baby, and Amy, who is marrying one, her life is great.
When Leonard's mother, Beverly, phoned for him one day when he was out, she started talking to Penny. Following their personal conversation, Beverly and Penny started communicating often and formed a close bond. Leonard was freaked out by his wife's closeness with his distant mother. After he confronted his mother for telling Penny how proud she was of him, despite never saying anything like that to him, Beverly admitted she was proud of him for marrying well as Penny is the most impressive of her children's spouses.
After Sheldon reminded the guys about the time they mined Bitcoin without him, Leonard, Howard and Raj went on a quest to find their suddenly valuable missing cryptocurrency. When they realized the currency was on an old laptop which Leonard gave to Penny while they were dating, he was angry when he found out she gave it to her ex-boyfriend Zack. When Leonard and Penny went to Zack's apartment to retrieve the old laptop, he showed them a seven-year-old video that Penny had recorded on the laptop soon after she broke up with Leonard. Leonard was touched by the video which showed a drunk Penny lamenting the break-up of her relationship with him.
When Leonard received a braggy Christmas letter from his brother, he started to feel bad about how little he and Penny had achieved that year. Leonard wondered if he and Penny should be thinking about the next step after two years of marriage, like buying a house or having a baby. Penny told him she wanted to do all those things someday, but she had a bunch of stuff she would like to do first, but they could start doing them. After Leonard suggested a day trip to Catalina, Penny agreed they should do it.
Leonard had several short-lived relationships prior to Penny moving into the building. The first one with Joyce Kim, a North Korean spy, ended after she returned to North Korea. He also had a relationship with a French woman with a PhD in French Literature. After breaking up with Penny the first time, Leonard had several casual hook-ups over the next year: Dr. Elizabeth Plimpton, a scientist friend of Sheldon's; Joy, a woman Leonard was set up with by Bernadette; Priya, Raj's sister who was visiting LA; and Mrs. Latham, a wealthy widow who donates money to the university. He also had a night of sex with a drunken Penny, who regretted it, and almost had sex with her when the both of them were at a conference and ended up in the same bedroom - although Raj interrupted them.
As for longer relationships, after Penny first moved in to apartment 4B, Leonard abandoned hope of getting together with her when he saw her with another guy. In response, Leonard asked out Leslie Winkle, a fellow scientist from the university who greatly irritated Sheldon. She declined because a kiss between her and Leonard didn't arouse her. A few months later, Leslie seduced Leonard, but this dalliance was short-lived as Leslie wasn't interested in a long-term relationship and Leonard was. After Leonard's ultimately unsuccessful date with Penny, Leslie decided she wanted a long-term partner but after a few dates, she decided Leonard wasn't a suitable mate because of a scientific disagreement.
Leonard then met Dr. Stephanie Barnett, a girl Howard initially picked up, but who had no interest in Howard. Leonard and Stephanie's relationship was going well, and even Sheldon was impressed with her. When Sheldon tried to activate a section of the roommate agreement related to cohabitation and Penny pointed out the changes in Leonard's room, Leonard realized that Stephanie had moved in without his noticing. Fearing their relationship was moving too fast, Leonard tried to break up with her — but each time just led to sex. Finally, Leonard told her to move out by texting her. Leonard thought it would end the relationship, but she texted him back, offering to have sex with him. The relationship was apparently set to continue, however Stephanie hasn't been seen again.
After the first time Priya visited L.A., she moved to Pasadena to work in the US for her company. After some discussion, Leonard and her started an actual relationship, instead of their previous one night stands. When Priya, being a lawyer, pointed out problems with Sheldon's roommate agreement, he was unhappy that his ability to control his friends was taken away. Sheldon then blackmailed Priya, warning her he would tell her parents she was dating Leonard, unless he signed a new roommate agreement.
Priya tried to force changes on Leonard, including how he dressed and making him wear contact lenses. But the biggest change she tried to force on him was demanding he stay away from Penny. Priya, worried again about what they might think of her dating a non-Indian person, kept her relationship with Leonard a secret from her parents, causing Leonard to question whether she was ashamed of him. Still, Leonard and Priya did discuss plans of traveling to India, so Leonard could meet her parents.
Leonard accidentally found out Priya would be moving back to India, something she hadn't told him yet. Although he was angry she hadn't discussed it with him, they worked through that and tried to continue their relationship long distance, although their attempts at cyber-sex were dismal failures.
During his long distance relationship with Priya, Leonard met a comic book artist, Alice, who shared many of Leonard's interests. They hit it off and, when they were looking over comic books together, Alice kissed Leonard and he returned the kiss. Leonard was torn over whether he should have sex with her while he was still in a relationship with Priya. After going to Alice's apartment, they started kissing but Leonard ultimately decided to be a "good guy" and not sleep with Alice. When Leonard told Priya about Alice and his decision not to sleep with her, Priya revealed she had already slept with her previous boyfriend, so Leonard ended their relationship.
Living with Sheldon
Sheldon is Leonard's best friend and long-time roommate, however living with him and being his friend is not without its difficulties for Leonard. While Leonard does his best to appreciate Sheldon's quirks and eccentricities, he does sometimes lose his temper when Sheldon is especially annoying. Leonard not only has to put up with Sheldon's quirks and demands, he also has to perform a lot of errands for Sheldon. Since Sheldon did not drive, Leonard would drive Sheldon to work and the comic book store, among other places.
Sheldon though, has come through for his buddy at various times. Sheldon helped Leonard confront Penny's ex-boyfriend, Kurt; asked Penny not to hurt his friend, and saved Leonard from exploding rocket fuel. When Professor Proton asked Leonard why he put up with Sheldon, Leonard told him how Sheldon can be aggravating but that he isn't doing it on purpose. When Professor Proton pushed him for more, Leonard said Sheldon is loyal, trustworthy and that they have fun together. Leonard called Sheldon the smartest person he knew, and pointed out Sheldon a little broken and needs him. Then Leonard admitted he needs Sheldon, too.
Leonard has, at times, threatened to leave Sheldon rather than submit to his will or the roommate agreement. Sheldon annoyed him by waking him up in the middle of the night for an apartment safety drill, leading Leonard to nullify their friendship. They made up when Sheldon promised Leonard his own special day. Later, after Sheldon spoiled the Harry Potter books for Leonard, he temporarily moved in with Penny, until Penny explained she wasn't ready to live together yet.
When Leonard pointed out to Sheldon that he was the only reason Leonard wasn't living with his fiancé, Sheldon agreed to let Leonard gradually start moving out. They started with Leonard staying with Penny one day a week, though Sheldon slept over at Penny's apartment with them. They later had disagreement over each other's role in a scientific paper they wrote together. After Sheldon moved out to live with Amy, they disagreed over how to split their shared possessions.
After Sheldon and Amy put their friends through a series of tests to see who should be their best man and maid of honor, their friends were outraged when they found out. When Sheldon briefly made Stuart his best man to avoid upsetting his friends who’d turned against him, Leonard told Sheldon that he could pick anyone he wants for his best man and doesn't need to worry about anyone else. Sheldon eventually apologized to Leonard for the tests and made him his best man.
When he needed a place to work away from Amy, Sheldon rented his old room back from Leonard and Penny. Despite Leonard’s fears that Sheldon would be just as annoying as he was as a roommate, Sheldon turned out to be the model tenant. Leonard grew increasingly irritated that Sheldon can seemingly be considerate when he wants to be. When Leonard tried to evict him under the tenancy agreement that Sheldon drew up, he got a reminder of the old Sheldon in the form of a sneaky loophole in the agreement. Although Leonard failed to dislodge Sheldon from the apartment, he was relieved to once again be dealing with the irritating Sheldon he was familiar with.
When Leonard and Penny suspected that it was Sheldon who complained to the Tenants’ Association about a food truck parked outside the apartment building, they were surprised to find he was the tenants’ association. With the reluctant help of Amy, Leonard successfully challenged Sheldon’s reign as president. As Sheldon handed power over to Leonard, promising instead to be the vocal opposition “criticizing and badgering the president at every turn”, Leonard realized he had made a huge mistake.
At Sheldon and Amy’s wedding, Leonard emotionally told Sheldon how happy he was for him, and for himself as Sheldon was now officially - and legally - Amy’s problem. Sheldon insisted that he will always be Leonard’s problem. Later, Leonard found Sheldon and Amy working on a new theory of super asymmetry. Despite it holding up the wedding, Leonard stayed with the soon-to-be-wed couple to work on their interesting development.
Leonard has been shown to have close friendships with Howard and Raj, both of whom were his friends before he met Sheldon. It was through Leonard that they both met Sheldon. Leonard has, at times, been Howard's wingman, though after spending a night on the town with Howard, Leonard started to question whether Howard saw nearly as much action as he claimed. Howard also called on Leonard to take home a woman he had met at a bar, Stephanie, and Leonard ended up dating her. When Howard called on a pact he had with Leonard, Leonard asked Penny to set Howard up with one of her friends. Penny introduced Howard to Bernadette, at that time her co-worker at the Cheesecake Factory. Things worked well between them and Bernadette is now Howard's wife.
Leonard's friendship with Raj encountered trouble when Leonard started dating Priya. Raj was very unhappy about the relationship and having to sleep on his own couch. Leonard and Raj swapped apartments, which led to an evening where he and Penny got drunk, ending up in bed together. While Leonard was angry at Raj for sleeping with his ex, he was more upset that Raj didn't tell him Priya was going back to India. Although things between them were tense for a while, they worked things out, to the point of Leonard asking Raj to stay with him and Penny when Raj was forced to move out of his apartment. When Raj was tasked with recording a message for a NASA mission outside the solar system, Raj and Leonard bonded over their role as the "omega males" in the group, feeling they were often pushed around by "alpha males" Sheldon and Howard.
One other friend of Leonard's, while not as close as Raj and Howard, is Stuart Bloom, who runs the comic book store the guys frequent. Leonard pushed to have Stuart join the group when Howard was in space and offered, with the other guys, helping finance Stuart's new store. Their friendship was a bit strained at one point when Stuart went out with Penny on two dates. Leonard did find out that Penny called out his name while kissing Stuart.
When Sheldon threw Amy out of the apartment so he could work alone, Amy started hanging out with Leonard and Penny in their apartment. Amy and Leonard bonded over their history of being spelling bee champions and later performed a series of science experiments together.
Leonard graduated from high school at sixteen and earned his PhD from Princeton at the still relatively young age of 24. He is currently an experimental physicist at Caltech, specializing in lasers and sub atomic measurements using lasers. In his early years at Caltech, he worked on developing various rocket fuels. When Dr Arthur Jeffries (AKA Professor Proton) wrote a paper on nano-vacuum tubes, he asked Leonard to review it and then collaborate with him on experimental testing of his hypothesis.
Howard recommended Leonard for a job with a group gathered by Stephen Hawking for a scientific trip to the North Sea. He spent four months working on board a ship, testing Hawking's hypothesis that large bodies of water could provide a hydrodynamic simulation of black holes. When Sheldon developed a hypothesis to create super-heavy elements, a Chinese team found the predicted element. However, Sheldon discovered an error in his hypothesis and was puzzled as to how the Chinese team found it. Leonard ran his own experiments and provided the experimental data that showed the Chinese teams discovery was a hoax and Sheldon's method was invalid.
Besides his work proving Sheldon's hypothesis wrong, Leonard has occasionally worked with Sheldon, often with mixed results. After Sheldon and Leonard wrote a paper on super-solids, Sheldon received a letter asking them to present their paper at a physics conference. Sheldon threw the letter away without asking Leonard, who later decided to present the paper without Sheldon. Sheldon showed up at Leonard's presentation and derailed it, leading to a physical fight between him and Leonard that ended up on YouTube.
After Leonard had an idea to look at the universe as the surface of a super fluid, he showed it to Sheldon and as a result, he and Sheldon co-wrote a paper and published it online. It got many good comments and even won the approval of Stephen Hawking, and the paper was later mentioned in Scientific American. However, Scientific American listed the paper as being from Sheldon Cooper and his team. Leonard became upset that he was demoted to being Sheldon's team and that his contribution to the paper was not acknowledged.
When Leonard, Sheldon and Howard worked on way to get more women into scientific fields, they gave a talk to middle school girls to try get them interested in careers in science. After Leonard was asked to give the commencement speech at his old high school in New Jersey, bad weather almost had him cancel the speech. Penny was able to arrange for Leonard to give the speech via Skype from his apartment. After boring even himself with his prepared notes, he finally just told the kids that if they didn't have friends or fit in, the things they were doing in school, such as learning an instrument or building computers, would make them interesting later in life.
After Leonard gave a downbeat assessment of the state of physics on the radio, he feared losing his job at the university and grew increasingly depressed about his job prospects and the future of physics. When Leonard's friends couldn't cheer him up, the guys drowned their sorrows with Romulan ale before visiting Richard Feynman's grave to celebrate the iconic physicist.
Leonard and Howard were angered to find out that Sheldon was working with the military on their gyroscope project behind their backs. After he and Howard had an idea to make their guidance system better, they decided to get back at Sheldon by shopping their improved idea to the military without him. Unfortunately, Leonard and Howard needed somebody to figure out the math, so they turned to Barry Kripke, who ultimately took the idea to the military on his own.
- Full name: Leonard Leakey Hofstadter.
- Born: May 1980.
- Leonard and Sheldon are both named after the famed TV producer and actor Sheldon Leonard.
- Leonard gets his middle name from Professor Louis Leakey.
- Leonard's last name is in honor of Nobel Prize winning physicist Robert Hofstadter, who worked at Stanford University in the field of nuclear physics.
- Although Leonard's IQ has not directly been mentioned on the show, he and Sheldon have said they have a combined IQ of 360. Sheldon has said his IQ is 187. Therefore, Leonard's IQ is 173.
- Leonard is lactose-intolerant and can not process corn.
This page has been updated to episode 1124. The Bow Tie Asymmetry
Leonard: Hang on, if you're making all this money, where is it?
Penny: In a safe place.
Leonard: What does that mean, under your bed?
Penny: No, it means a diversified portfolio of stocks and bonds. I'm not overly conservative. I'm young, so my guy said I can afford to take some risks.
Leonard: Wait a minute, you have "a guy"?
Penny: Don't you have a guy?
Leonard: Why would I have a guy?! I don't have any money!
Leonard: My point is, while you're spending all this time on your own, building computers or practicing your cello, what you're really doing is becoming interesting. When people finally do notice you, they're gonna find someone a lot cooler than they thought. And for those of you that were popular in high school, it's over, sorry. Thank you. Congratulations.
Penny: Well you wouldn't have asked me either.
Leonard: I would have asked you. In my head. On the way home. While I was having a good cry.
Leonard: You know what, this bottle was meant to celebrate an achievement. Let's make a pact. When one of us gets their first big breakthrough, we'll celebrate by opening this bottle and toasting Professor Abbott.
Howard: I love that.
Raj: Me too.
Leonard: Then, of course, rubbing our success in Sheldon's face.
Howard: Well that's the best part.
Sheldon: This song is never going to stop. Have you ever dealt with something so relentlessly irritating?
Leonard: That's a trick question, right?
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