high tide vs neap

high tide and neap both are nouns.

Word	Noun	Adjective	Verb	Adverb
high tide	Yes	No	No	No
neap	Yes	No	No	No

As nouns, neap is a hyponym of high tide; that is, neap is a word with a more specific, narrower meaning than high tide:

high tide: the tide when the water is highest
neap: a less than average tide occurring at the first and third quarters of the moon

Other hyponyms of high tide include direct tide, neap tide, springtide.

high tide (noun)	neap (noun)
the tide when the water is highest	a less than average tide occurring at the first and third quarters of the moon