past perfect vs perfect tense

past perfect and perfect tense both are nouns.

Word	Noun	Adjective	Verb	Adverb
past perfect	Yes	No	No	No
perfect tense	Yes	No	No	No

As nouns, perfect tense is a hypernym of past perfect; that is, perfect tense is a word with a broader meaning than past perfect:

past perfect: a perfective tense used to express action completed in the past
perfect tense: a tense of verbs used in describing action that has been completed (sometimes regarded as perfective aspect)

Other hypernyms of past perfect include perfect, perfective, perfective tense.

past perfect (noun)	perfect tense (noun)
a perfective tense used to express action completed in the past	a tense of verbs used in describing action that has been completed (sometimes regarded as perfective aspect)