A tree house is a small structure built among the branches of a tree, usually as a play space or hideout. Kids climb up into their tree house using a ladder, rope, or wooden steps nailed to the trunk, finding a secret world above the ground where they can read, play games, or just watch the world from their elevated perch.

Building a tree house requires choosing a strong tree with sturdy branches, then constructing a platform and walls that won't harm the tree as it grows. Some tree houses are simple platforms with a railing, while others have roofs, windows, and even furniture. The best tree houses feel like a private clubhouse suspended in the leaves, where you can spot birds at eye level and feel the gentle sway of the tree in the breeze.

The two-word term is sometimes written as one word, treehouse, and occasionally hyphenated as tree-house. Beyond actual structures in trees, people use the phrase for any elevated hideaway: architects design elaborate tree house hotels for adventurous travelers, and anyone seeking escape might joke about running away to live in a tree house.