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.

D is for dual, a common notion in graph theory. See also the follow-up post referring to this article on Saving School Math.

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.

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*Posted by John Quintanilla on September 11, 2015*

https://meangreenmath.com/2015/09/11/mathematics-a-to-z-part-1/

## Joseph Nebus

/ September 17, 2015I’m embarrassed to be so late acknowledging these. Thanks for paying and bringing some attention to my little blog; I’m flattered.