sharpen vs focus

sharpen is not a noun while focus is a noun.

Word	Noun	Adjective	Verb	Adverb
sharpen	No	No	Yes	No
focus	Yes	No	Yes	No

As verbs, sharpen and focus are synonyms defined as:

Other synonyms of sharpen include focalise, focalize.

As verbs, focus is a hyponym of sharpen; that is, focus is a word with a more specific, narrower meaning than sharpen:

sharpen (noun)	focus (noun)
	maximum clarity or distinctness of an image rendered by an optical system
	maximum clarity or distinctness of an idea
	the concentration of attention or energy on something
	a fixed reference point on the concave side of a conic section
	a point of convergence of light (or other radiation) or a point from which it diverges
	a central point or locus of an infection in an organism
	special emphasis attached to something

sharpen (verb)	focus (verb)
become sharp or sharper	become focussed or come into focus
make crisp or more crisp and precise	put (an image) into focus
raise the pitch of (musical notes)	direct one's attention on something
put (an image) into focus	bring into focus or alignment; to converge or cause to converge; of ideas or emotions
make (one's senses) more acute	cause to converge on or toward a central point
give a point to
make sharp or sharper
make (images or sounds) sharp or sharper