headgear vs clothing

headgear and clothing both are nouns.

Word	Noun	Adjective	Verb	Adverb
headgear	Yes	No	No	No
clothing	Yes	No	No	No

As nouns, clothing is a hypernym of headgear; that is, clothing is a word with a broader meaning than headgear:

Other hypernyms of headgear include article of clothing, habiliment, vesture, wear, wearable.

headgear (noun)	clothing (noun)
clothing for the head	a covering designed to be worn on a person's body
stable gear consisting of any part of a harness that fits about the horse's head
the hoist at the pithead of a mine