To approximate means to come close to the exact amount, value, or description of something without being perfectly precise. When you approximate your age to the nearest year, you might say “I'm ten” even if your birthday was six months ago. When a scientist approximates the distance to a star, she calculates a number that's close enough to be useful, even though measuring the exact distance down to the inch would be impossible.

Approximations are everywhere in daily life. When you estimate how long your homework will take, you're making an approximation. When a recipe calls for approximately two cups of flour, it means you don't need to be exact to the last grain. Weather forecasters approximate tomorrow's temperature, and builders approximate how much lumber they'll need for a project.

The related word approximate (pronounced slightly differently) works as an adjective meaning “close to but not exactly.” An approximate answer on a math test might be close to the right number but not precise. Scientists often report approximate values because perfect precision isn't always possible or necessary. Sometimes an approximation is good enough to solve a problem, make a decision, or understand what's happening. Learning when you need precision and when an approximation will do is an important skill in both math and life.