In greek mythology what is a tree nymph or tree spirit called?

In Greek mythology, a tree nymph or tree spirit is called a "dryad." Dryads are considered to be female spirits associated with oak trees, although the term can also refer to nymphs of other types of trees. They are often depicted as beautiful maidens and are believed to be protectors of their trees, with their lives closely tied to them; if the tree is harmed, so is the dryad.