A matrix is a rectangular grid of numbers arranged in rows and columns, like a spreadsheet with numbers instead of words. Mathematicians use matrices (that's the plural) to solve complex problems, especially when dealing with multiple equations at once. Think of a matrix as an organized way to keep track of lots of information: a teacher might use one to record every student's test scores across the whole year, with each row representing a student and each column representing a test.

Scientists and engineers use matrices to model everything from traffic flow in cities to how populations grow over time.

A matrix can also mean a material that supports or holds something else in place. For example, the tissue between cells in an animal's body is called the extracellular matrix.