tending vs first aid

tending and first aid both are nouns.

Word	Noun	Adjective	Verb	Adverb
tending	Yes	Yes	No	No
first aid	Yes	No	No	No

As nouns, first aid is a hyponym of tending; that is, first aid is a word with a more specific, narrower meaning than tending:

tending: the work of providing treatment for or attending to someone or something
first aid: emergency care given before regular medical aid can be obtained

tending (noun)	first aid (noun)
the work of providing treatment for or attending to someone or something	emergency care given before regular medical aid can be obtained

tending (adjective)	first aid (adjective)
(usually followed by `to') naturally disposed toward