sweet pepper plant vs sweet pepper

sweet pepper plant and sweet pepper both are nouns.

Word	Noun	Adjective	Verb	Adverb
sweet pepper plant	Yes	No	No	No
sweet pepper	Yes	No	No	No

As nouns, sweet pepper plant and sweet pepper are synonyms defined as:

sweet pepper plant and sweet pepper: plant bearing large mild thick-walled usually bell-shaped fruits; the principal salad peppers

Other synonyms of sweet pepper plant include bell pepper, Capsicum annuum grossum, paprika, pimento, pimiento.

sweet pepper plant (noun)	sweet pepper (noun)
plant bearing large mild thick-walled usually bell-shaped fruits; the principal salad peppers	large mild crisp thick-walled capsicum peppers usually bell-shaped or somewhat oblong; commonly used in salads
	plant bearing large mild thick-walled usually bell-shaped fruits; the principal salad peppers