high vowel vs close vowel

high vowel and close vowel both are nouns.

Word	Noun	Adjective	Verb	Adverb
high vowel	Yes	No	No	No
close vowel	Yes	No	No	No

As nouns, high vowel and close vowel are synonyms defined as:

high vowel and close vowel: a vowel sound made with your tongue near the top of your mouth.

high vowel (noun)	close vowel (noun)
a vowel sound made with your tongue near the top of your mouth.	a vowel sound made with your tongue near the top of your mouth.