Commutator Memes

The eternal mathematical crisis of notation! The poor mathematician is faced with two completely different definitions of the interval [a,b]. One button says it equals "ab - ba" (which would be zero if a and b commute), while the other defines it as the set of all real numbers between a and b. This is the mathematical equivalent of finding out your favorite restaurant has two completely different dishes with the same name. No wonder our friend is sweating bullets—imagine building an entire proof only to realize you've been using the wrong definition the whole time!