- A value which is guessed or estimated to be near, but not exactly correct.
- A result that is not necessarily precisely correct, but is accurate enough for a stated purpose.
Season 3, Episode 14 - The Einstein Approximation
Aired February 1, 2010
When Sheldon's struggle with a physics problem keeps him awake for days on end, he decides to free his mind by taking a menial job. After failing to find gainful employment anywhere else, Sheldon starts work at the Cheesecake Factory with Penny.
Season 4, Episode 18 - The Prestidigitation Approximation
Aired March 10, 2011
Priya feels threatened by Leonard spending time with Penny and demands he cut her out of his life. Leonard struggles to choose between his girlfriend and Penny. Meanwhile, Howard plays mind games with Sheldon by performing a magic trick the great scientist can not figure out.
Season 8, Episode 6 - The Expedition Approximation
Aired October 20, 2014
Sheldon and Raj consider applying for a dark matter research expedition in a salt mine, but their friends don't believe they would be able to cope with the difficult conditions. Sheldon and Raj test their hardiness to heat and cramped conditions in the university's steam tunnel.
Meanwhile, Leonard and Penny get into an argument over money. When they seek their married friends' help on how to handle their finances as a couple, it sparks a disagreement between Howard and Bernadette.
Season 9, Episode 4 - The 2003 Approximation
Aired October 12, 2015
When Sheldon learns that Leonard has moved out and is now living with Penny, he reverts to 2003 - a simpler time before he met Leonard and Penny. Howard and Raj form a folk sci-fi band to play live music at Stuart's Comic Book Store.