ink vs printer's ink

ink and printer's ink both are nouns.

Word	Noun	Adjective	Verb	Adverb
ink	Yes	No	Yes	No
printer's ink	Yes	No	No	No

As nouns, printer's ink is a hyponym of ink; that is, printer's ink is a word with a more specific, narrower meaning than ink:

ink: a liquid used for printing or writing or drawing
printer's ink: a semisolid quick drying ink made especially for use in printing

Other hyponyms of ink include indelible ink, drawing ink, India ink, magnetic ink, printing ink, writing ink.

ink (noun)	printer's ink (noun)
dark protective fluid ejected into the water by cuttlefish and other cephalopods	a semisolid quick drying ink made especially for use in printing
a liquid used for printing or writing or drawing

ink (verb)	printer's ink (verb)
fill with ink
mark, coat, cover, or stain with ink
append one's signature to