A bough is a large, thick branch of a tree, especially one of the main branches that grows directly from the trunk. When you climb a sturdy oak tree and sit on one of those big branches strong enough to hold your weight, you're sitting on a bough.

The word often appears in poems and songs because it sounds more musical than just saying “branch.” You might remember it from the lullaby “Rock-a-bye Baby,” which mentions a cradle rocking “in the treetop” when “the bough breaks.” That's talking about one of those substantial branches, not a thin twig.

Boughs are what give a tree its broad, spreading shape. In an apple orchard, heavy boughs bend downward when loaded with ripe fruit. During winter, thick boughs hold up layers of snow. Unlike smaller branches and twigs that snap easily, boughs are the tree's strong framework, sometimes as thick as your leg or even thicker. When you picture a perfect climbing tree with branches you could actually sit on, you're picturing its boughs.