• In mathematics and statistical methods, a tree diagram is used to determine the probability of getting specific results where the possibilities are nested. Example
• In physics, a tree diagram is an acyclic connected Feynman diagram.
• In linguistics, a parse tree is one way to visually represent the structure of a sentence (see X-bar theory), a syllable, or phonological feature geometry.
• In biology: phylogenetics.
• A game tree is a tree diagram used to find and analyze potential moves in a game.
• A decision tree is used in operations research.
• A HyperbolicTree: a visualization method for a graph inspired by hyperbolic geometry.

See also Tree (disambiguation) for tree structures which may not involve diagrams.