The word math comes from a shortening of mathematics. This is often what math is formally called when it’s a school subject. In the U.K. and other places, it’s shortened to maths. (See more about this in the next two sections.)

The type of math you learn early in school—addition, subtraction, multiplication, and division—is sometimes called arithmetic. It all starts with basic counting, but there are many branches of math, including algebra, geometry, and trigonometry, and calculus.

The word calculus is also sometimes used in a general way to mean calculation, and the word math can also be used in this way.

The word math is also used in other general ways. If you say the math doesn’t add up, it means something’s not right with the numbers (figures, values, totals, tally, etc.).

Math is short for mathematics.

In the U.S. and Canada, the school subject is commonly called math. In the U.K. and some other places, it’s called maths. To people who use the word math, it may seem strange to put an s on the end, since it’s a single subject, but there are plenty of reasons why it makes sense: it’s short for mathematics, there are several different branches of mathematics, and other school subjects also end with s, such as physics.

To do the math is to do the calculation, computation, or reckoning. This can be used in a literal way, meaning to literally calculate the sum or total. But it’s also often used in a figurative way meaning to figure something out based on the available information. The expression add things up can mean the same thing.