axis vs rotor head

axis and rotor head both are nouns.

Word	Noun	Adjective	Verb	Adverb
axis	Yes	No	No	No
rotor head	Yes	No	No	No

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

Other hyponyms of axis include pin, pivot, rotor shaft.

axis (noun)	rotor head (noun)
the center around which something rotates	the axis around which the major rotor of a helicopter turns
the 2nd cervical vertebra; serves as a pivot for turning the head
a straight line through a body or figure that satisfies certain conditions
a group of countries in special alliance
the main stem or central part about which plant organs or plant parts such as branches are arranged