armature vs rotor coil

armature and rotor coil both are nouns.

Word	Noun	Adjective	Verb	Adverb
armature	Yes	No	No	No
rotor coil	Yes	No	No	No

As nouns, rotor coil is a hyponym of armature; that is, rotor coil is a word with a more specific, narrower meaning than armature:

armature: coil in which voltage is induced by motion through a magnetic field
rotor coil: the rotating armature of a motor or generator

Other hyponyms of armature include rotor.

armature (noun)	rotor coil (noun)
coil in which voltage is induced by motion through a magnetic field	the rotating armature of a motor or generator