Last summer, Nebus Research had a fun series on the definitions of 26 different mathematical terms, one for each letter of the alphabet. Here are the words from A to E:
A is for ansatz, a uniquely mathematical bit of lingo.
B is for bijection, which I called a one-to-one correspondence when I was a student in the 1980s-1990s. This is a fundamental notion in real analysis and explains why there are exactly as many integers as there are rational numbers, even though the integers are a proper subset of the rational numbers.
C is for characteristic function, which only takes values of 0 and 1. This is similar to an indicator random variable in probability but is different than the characteristic equation encountered in differential equations.
E is for error, not in the sense of “a mistake,” but in the sense of the difference between a number and a partial sum of an infinite series whose sum is that number.