An inch is a unit of measurement equal to 1/12 of a foot, used mainly in the United States to measure length and distance. If you hold your thumb sideways, the width from the tip to the first joint is roughly an inch. A standard pencil is about 7.5 inches long, and a ruler typically measures 12 inches (one foot).

While most of the world uses the metric system (centimeters and meters), Americans still measure height, furniture, screen sizes, and countless other things in inches. An inch equals exactly 2.54 centimeters if you need to convert between systems.

The word inch can also mean to move forward very slowly and carefully. You might inch closer to the edge of a diving board, taking tiny steps because you're nervous. A car might inch through heavy traffic, moving forward bit by bit. When you're almost finished with something difficult, people say you're inching toward completion. This meaning captures that careful, gradual movement, as if you're moving forward one small inch at a time.