Is willow tree inflection or dervation?

The term "willow tree" involves derivation. The Word "willow" is derived from Old English "welig," while "tree" comes from Old English "treow." In this case, "willow" serves as a modifier for "tree," creating a specific type of tree rather than a grammatical inflection of a single Word. Inflection typically alters a Word to express different grammatical features, while derivation creates new Words or phrases.