Ordinal describes numbers that show position or order in a sequence, like first, second, third, and so on. When runners cross the finish line, you might say the fastest runner finished first, the next finished second, and another finished third. These are ordinal numbers because they tell you the order things happened in.

Contrast ordinal numbers with cardinal numbers, which tell you “how many” of something: one apple, two cats, three pencils. Cardinal numbers count quantity. Ordinal numbers show rank or sequence: the first apple you ate, the second cat you met, the third pencil in the row.

You use ordinal numbers constantly without thinking about it. When you say “I live on the fifth floor” or “That was my tenth time riding that roller coaster” or “She's in fourth grade,” you're using ordinals to show position in a sequence.

In writing, ordinals often appear with letters attached: 1st, 2nd, 3rd, 4th. Say these out loud and you'll hear why: first, second, third, fourth. The “st,” “nd,” “rd,” and “th” are the endings of the ordinal words.

Mathematicians and computer scientists also use ordinal in more technical ways to describe different types of infinity and ordering systems, but the basic idea remains the same: showing where something falls in a sequence.