Appearances in The Big Bang Theory
Sheldon uses Latin phrase "reductio ad absurdum" (literally "reduction to absurdity") in "The Dumpling Paradox" (S1E07), "post hoc, ergo propter hoc" (literally "after this, therefore because of this") in "The Electric Can Opener Fluctuation" (S3E01), "cathedra mea, regulae meae" (literally "My chair, my rules") in "The Staircase Implementation" (S3E22), "ipso facto" (literally "by the fact itself") in "The Zazzy Substitution" (S4E03) and "summa cum laude" (literally "with highest honor", usually meaning the highest degree that one has achieved) in "The Pants Alternative" (S3E18) and "The Higgs Boson Observation" (S6E03).
In "The Jiminy Conjecture" (S3E02), both Sheldon and Howard are shown to know the Latin names of insect species. Also, Sheldon either remembers particular Latin quotes or demonstrates his ability to translate short phrases into Latin.
- Howard: The common field cricket, AKA Gryllus assimilis, which is Latin for "suck it, you lose".
- Sheldon: The snowy tree cricket. AKA, Oecanthus fultoni, which is Latin for "I'll suck nothing". Of course I'm joking because the Latin for that is nihil exsorbebo.
In "The Excelsior Acquisition" (S3E016), Sheldon pleads his own case in traffic court for speeding, while taking Penny to the hospital (in S3E08 "The Adhesive Duck Deficiency"), using the phrase quod est necessarium est licitum, Latin for "what is necessary is lawful".
In pleading his case against a traffic camera (representing himself of course), he uses the phrase