Thin means having little distance between two opposite sides or surfaces. A thin piece of paper is easy to tear because there isn't much material between its front and back. A thin rope might snap under heavy weight, while a thick rope holds strong. When you slice bread thinly, you can see light through it.

The word also describes people or animals with little body fat or flesh. A thin runner might move quickly because they're carrying less weight, while a thin tree branch might bend easily in the wind. When something becomes thinner over time, we say it thins out: your patience might wear thin after hearing the same excuse repeatedly, or a crowd thins out as people leave.

Thin can describe other qualities too. A thin excuse is weak and unconvincing, one that doesn't hold up under questioning. Thin soup has lots of water and few ingredients. The phrase thin-skinned describes someone who gets hurt feelings easily, as if their emotional protection is too thin to shield them from criticism.

The opposite of thin is thick or fat. Something can be paper-thin, razor-thin, or thin as a rail. When ice on a pond is too thin, it's dangerous to skate on because it might crack under your weight.