noun A perennial woody plant taller and larger than a shrub with a wooden trunk and, at some distance from the ground, having leaves and branches.
Hyperion is the tallest living tree in the world.
noun Any other plant (such as a large shrub or herb) that is reminiscent of the above in form and size.
The banana tree is a tall perennial herb: its trunk is not woody.
noun An object made from a tree trunk and having multiple hooks or storage platforms.
He had the choice of buying a scratching post or a cat tree.
noun A device used to hold or stretch a shoe open.
He put a shoe tree in each of his shoes.
noun The structural frame of a saddle.
noun A connected graph with no cycles or, if the graph is finite, equivalently a connected graph with n vertices and n−1 edges.
noun A recursive data structure in which each node has zero or more nodes as children, but does not share children with other nodes.
noun A display or listing of entries or elements such that there are primary and secondary entries shown, usually linked by drawn lines or by indenting to the right.