A number is a concept we use to count, measure, and compare quantities. When you have three apples, seven pencils, or twelve friends at your birthday party, you're using numbers to describe how many of something you have.

Numbers form the foundation of mathematics. They let us answer questions like “How many?” and “How much?” You use them constantly: checking the time (3:45), measuring ingredients (2 cups of flour), scoring games (21 to 18), or counting money ($15.37).

Numbers come in different types. Whole numbers like 1, 2, 3 are what you first learn to count with. Fractions like ½ or ¾ describe parts of things. Decimals like 3.14 are another way to express parts. Negative numbers like -5 fall below zero, useful for temperatures or bank balances. Even zero is a number, representing nothing, and it took civilizations thousands of years to invent the concept.

The word also appears in phrases like “your number is up” (your time has come) or doing something “by the numbers” (following exact steps). A singer's “big number” in a musical means their main song. And when something is numbered, it has numbers assigned to it, like the pages in a book or houses on a street.

As a verb, number means to give something a number or put things in order using numbers, like numbering the questions on a worksheet.