Piper nigrum vs true pepper

Piper nigrum and true pepper both are nouns.

Word	Noun	Adjective	Verb	Adverb
Piper nigrum	Yes	No	No	No
true pepper	Yes	No	No	No

As nouns, true pepper is a hypernym of Piper nigrum; that is, true pepper is a word with a broader meaning than Piper nigrum:

Piper nigrum: climber having dark red berries (peppercorns) when fully ripe; southern India and Sri Lanka; naturalized in northern Burma and Assam
true pepper: any of various shrubby vines of the genus Piper

Other hypernyms of Piper nigrum include pepper vine.

Piper nigrum (noun)	true pepper (noun)
climber having dark red berries (peppercorns) when fully ripe; southern India and Sri Lanka; naturalized in northern Burma and Assam	any of various shrubby vines of the genus Piper