one-letter
Explanation
The Joke
The caption reads: "Fun fact: It's possible to make a pantsless mathematician cry using a single letter." The scene shows what appears to be a romantic or intimate moment between two people -- they are in a bedroom, and both are in states of undress. One person says the Greek letter epsilon (the symbol used in analysis proofs). The mathematician's expression immediately shifts to one of distress and dread.
The joke is that the Greek letter epsilon is deeply associated with the notoriously difficult and tedious epsilon-delta proofs in real analysis, a subject that is often the bane of mathematics students and even professional mathematicians. Even in a romantic moment, simply hearing "epsilon" is enough to trigger traumatic flashbacks to grueling proof-writing.
The Humor
The humor works because of the incongruity between the intimate setting and the mathematical trauma. The idea that a single Greek letter could ruin the mood and reduce a mathematician to tears is both absurd and relatable to anyone who has struggled through a real analysis course. The specification that the mathematician is "pantsless" emphasizes that this is supposed to be a moment of vulnerability and intimacy, making the emotional devastation caused by a single letter all the funnier.
References
Epsilon is conventionally used in mathematical analysis to represent an arbitrarily small positive quantity. The epsilon-delta definition of a limit, formalized by Karl Weierstrass in the 19th century, is a foundational concept in calculus and real analysis. It is notorious among math students for being conceptually challenging and requiring meticulous, detail-oriented proofs. The phrase "for all epsilon greater than zero, there exists a delta..." is the beginning of many a mathematician's nightmare.