Crease means a line or ridge made by folding, pressing, or wrinkling something. When you fold a piece of paper in half and press down hard, the crease shows exactly where you folded it. Your pants might have a sharp crease down the front of each leg from being ironed. A crease can also form on your forehead when you scrunch up your face while thinking hard or feeling worried.

The word works as a verb too: you can crease paper when folding origami, or accidentally crease a poster you're trying to keep flat. In cricket, batters stand behind marked creases at each end of the pitch.

Some creases show care and attention, like the crisp creases in dress clothes or a carefully folded letter. Other creases reveal age and use, like the soft creases in a beloved book you've read dozens of times. Still others appear on your skin when you smile, laugh, or concentrate, showing the expressions you make most often.