Sheldon Cooper's use of the word "coitus" as a clinical term for sex is explained in "Young Sheldon" Season 5, Episode 6, where he searches for a more acceptable word to use in conversations about human reproduction. Despite partaking in "coitus" with Amy Farrah Fowler on her birthday each year, Sheldon's mindset towards physical intimacy has not changed much since adolescence. Sex plays a small part in his life, and he does not understand the societal hype surrounding it. Nonetheless, his character's choice to opt-out of that part of life is one of the most wonderful things about him.
