This is the 670th most frequent Chinese word.
树
Tree.
The word '树' here is used as a noun to refer to a physical tree, a woody perennial plant.
这是一棵高大的树。
This is a tall tree.
The word '树' in this sentence is also a noun, indicating the location — under the tree.
我喜欢在树下读书。
I like reading under the tree.
The word '树' here, as a noun, is used to indicate multiple trees being planted as part of a verb-object combination.