eraser vs ink eraser

eraser and ink eraser both are nouns.

Word	Noun	Adjective	Verb	Adverb
eraser	Yes	No	No	No
ink eraser	Yes	No	No	No

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

Other hyponyms of eraser include blackboard eraser, pencil eraser, rubber, rubber eraser.

eraser (noun)	ink eraser (noun)
an implement used to erase something	an eraser that removes ink marks