Dryads (Δρυάδες, sing.: Δρυάς) are tree nymphs in Greek mythology. In Greek drys signifies 'oak,' from an Indo-European root *derew(o)- 'tree' or 'wood'. Thus dryads are specifically the nymphs of oak trees, though the term has come to be used for all tree nymphs in general. "Such deities are very much overshadowed by the divine figures defined through poetry and cult," Walter Burkert remarked of Greek nature deities. They were normally considered to be very shy creatures, except around the goddess Artemis, who was known to be a friend to most nymphs.
The dryads of ash trees were called the Meliai. The ash-tree sisters tended the infant Zeus in Rhea's Cretan cave. Rhea gave birth to the Meliai after being made fertile by the blood of castrated Ouranos. Nymphs associated with apple trees were Epimeliad, and walnut-trees Caryatids.
Dryads, like all nymphs, were supernaturally long-lived and tied to their homes, but some were a step beyond most nymphs. These were the hamadryads who were an integral part of their trees, such that if the tree died, the hamadryad associated with it died as well. For these reasons, dryads and the Greek gods punished any mortals who harmed trees without first propitiating the tree-nymphs.
Dryads are mentioned in Milton's Paradise Lost, in Coleridge, and in Thackeray's work The Virginians.. Keats addresses the nightingale as 'light winged Dryad of the trees', in his Ode to a Nightingale. In the poetry of Donald Davidson they illustrate the themes of tradition and the importance of the past to the present. The poet Sylvia Plath uses them to symbolize nature in her poetry in "On the Difficulty of Conjuring up a Dryad", and "On the Plethora of Dryads".