headgear vs article of clothing

headgear and article of clothing both are nouns.

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

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

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

headgear (noun)	article of 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