perimeter vs girth

perimeter and girth both are nouns.

Word	Noun	Adjective	Verb	Adverb
perimeter	Yes	No	No	No
girth	Yes	No	Yes	No

As nouns, girth is a hyponym of perimeter; that is, girth is a word with a more specific, narrower meaning than perimeter:

perimeter (noun)	girth (noun)
the size of something as given by the distance around it	stable gear consisting of a band around a horse's belly that holds the saddle in place
the boundary line or the area immediately inside the boundary	the distance around a person's body
a line enclosing a plane areas

perimeter (verb)	girth (verb)
	tie a cinch around