edge vs razor edge

edge and razor edge both are nouns.

Word	Noun	Adjective	Verb	Adverb
edge	Yes	No	Yes	No
razor edge	Yes	No	No	No

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

edge (noun)	razor edge (noun)
a sharp side formed by the intersection of two surfaces of an object	an edge that is as sharp as the cutting side of a razor
the outside limit of an object or area or surface; a place farthest away from the center of something
a slight competitive advantage
the attribute of urgency in tone of voice
the boundary of a surface
a line determining the limits of an area

edge (verb)	razor edge (verb)
lie adjacent to another or share a boundary
provide with an edge
advance slowly, as if by inches
provide with a border or edge