A fraction is a way of describing a part of something whole. When you cut a pizza into eight equal slices and take three of them, you've taken three-eighths (written as 3/8) of the pizza. The number on top, called the numerator, tells you how many parts you have. The number on the bottom, called the denominator, tells you how many equal parts make up the whole.

Fractions help us talk precisely about amounts that aren't whole numbers. If you and two friends split a candy bar equally, you each get one-third. If you've read 50 pages of a 200-page book, you've finished one-fourth (or 1/4) of it.

Understanding fractions means recognizing that 1/2 of a large pizza is more actual pizza than 3/4 of a tiny cupcake, even though three-quarters sounds like more than one-half. It also means seeing that 2/4, 3/6, and 1/2 are different ways of describing the exact same amount. These are called equivalent fractions.

Fractions appear everywhere: in recipes (1/2 cup of sugar), in time (a quarter past three), in measurements, in probabilities, and in countless other situations where whole numbers alone won't do the job.