border vs close in

border is a noun but close in is not a noun.

Word	Noun	Adjective	Verb	Adverb
border	Yes	No	Yes	No
close in	No	No	Yes	No

As verbs, close in is a hyponym of border; that is, close in is a word with a more specific, narrower meaning than border:

Other hyponyms of border include fringe, gird, girdle, cloister, enclose, inclose, shut in, hem in, cloister.

As verbs, close in is a hypernym of border; that is, close in is a word with a broader meaning than border:

Other hypernyms of border include enclose, inclose, shut in.

border (noun)	close in (noun)
a strip forming the outer edge of something
a decorative recessed or relieved surface on an edge
a line that indicates a boundary
the boundary of a surface
the boundary line or the area immediately inside the boundary

border (verb)	close in (verb)
lie adjacent to another or share a boundary	surround completely
extend on all sides of simultaneously; encircle	advance or converge on
enclose in or as if in a frame
provide with a border or edge
form the boundary of; be contiguous to