hydrostatics vs fluid mechanics

hydrostatics and fluid mechanics both are nouns.

Word	Noun	Adjective	Verb	Adverb
hydrostatics	Yes	No	No	No
fluid mechanics	Yes	No	No	No

As nouns, fluid mechanics is a hypernym of hydrostatics; that is, fluid mechanics is a word with a broader meaning than hydrostatics:

hydrostatics: study of the mechanical properties of fluids that are not in motion
fluid mechanics: study of the mechanics of fluids

Other hypernyms of hydrostatics include hydraulics.

hydrostatics (noun)	fluid mechanics (noun)
study of the mechanical properties of fluids that are not in motion	study of the mechanics of fluids