subsection vs segment

subsection and segment both are nouns.

Word	Noun	Adjective	Verb	Adverb
subsection	Yes	No	No	No
segment	Yes	No	Yes	No

As nouns, segment is a hypernym of subsection; that is, segment is a word with a broader meaning than subsection:

subsection: a section of a section; a part of a part; i.e., a part of something already divided
segment: one of several parts or pieces that fit with others to constitute a whole object

Other hypernyms of subsection include section.

subsection (noun)	segment (noun)
a section of a section; a part of a part; i.e., a part of something already divided	one of several parts or pieces that fit with others to constitute a whole object
	one of the parts into which something naturally divides

subsection (verb)	segment (verb)
	divide into segments
	divide or split up