sweet pepper plant vs bell pepper

sweet pepper plant and bell pepper both are nouns.

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

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

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

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

sweet pepper plant (noun)	bell pepper (noun)
plant bearing large mild thick-walled usually bell-shaped fruits; the principal salad peppers	large bell-shaped sweet pepper in green or red or yellow or orange or black varieties
	plant bearing large mild thick-walled usually bell-shaped fruits; the principal salad peppers