Measurement is the process of finding out how much or how many of something there is using numbers and units. When you measure your height in inches, weigh ingredients in cups for a recipe, or time how long it takes to run a mile, you're measuring.

Every measurement has two parts: a number and a unit. Saying you're “60” doesn't mean anything, but “60 inches tall” gives others a clear picture. The same distance could be measured as 5 feet, 60 inches, or about 1.5 meters. Different units work better for different situations: you'd measure the length of a pencil in inches, but the distance between cities in miles.

Measurement requires tools. Rulers measure length, scales measure weight or mass, clocks measure time, and thermometers measure temperature. Scientists use precise instruments to measure things like the speed of light or the mass of atoms, while construction workers use tape measures and levels to build houses that are safe and sturdy.

Accurate measurement requires care. If you're measuring flour for cookies and just guess instead of leveling off the measuring cup, your cookies might turn out wrong. Scientists repeat measurements multiple times to make sure they're accurate. When doctors measure your height and weight, that information helps them understand if you're growing properly. Throughout history, the ability to measure precisely has allowed humans to build bridges, navigate oceans, and send rockets to the Moon.