Why should you never argue with a 90-degree angle?

This joke hinges entirely on a clever bit of wordplay, a classic comedic mechanism that takes advantage of words with multiple meanings. In this case, the humor comes from the double entendre of the word "right." A 90-degree angle is, by definition, a "right" angle in geometry. Simultaneously, "right" also means correct or accurate, implying that the angle is always faultless in its reasoning. The setup leads you to think about an argument, then delivers a punchline that plays on the angle's inherent geometric characteristic.

The concept of a 90-degree angle is fundamental to our world, far beyond the pages of a math textbook. You see them everywhere: the corners of a room, the intersection of walls and floors, the precise construction of most buildings, and even the way your screen meets its frame. Architects, carpenters, and engineers rely on these perfectly perpendicular angles to ensure stability and precision. So, in a very literal and practical sense, these angles are indeed "always right" for keeping our structures sound and our world neatly aligned, making the joke's premise surprisingly grounded in reality.