high tide vs tide

high tide and tide both are nouns.

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

As nouns, tide is a hypernym of high tide; that is, tide is a word with a broader meaning than high tide:

high tide: the tide when the water is highest
tide: the periodic rise and fall of the sea level under the gravitational pull of the moon

high tide (noun)	tide (noun)
the tide when the water is highest	the periodic rise and fall of the sea level under the gravitational pull of the moon
	something that may increase or decrease (like the tides of the sea)
	there are usually two high and two low tides each day