periwinkle vs Catharanthus roseus

periwinkle and Catharanthus roseus both are nouns.

Word	Noun	Adjective	Verb	Adverb
periwinkle	Yes	No	No	No
Catharanthus roseus	Yes	No	No	No

As nouns, periwinkle and Catharanthus roseus are synonyms defined as:

periwinkle and Catharanthus roseus: commonly cultivated Old World woody herb having large pinkish to red flowers

periwinkle (noun)	Catharanthus roseus (noun)
edible marine gastropod	commonly cultivated Old World woody herb having large pinkish to red flowers
small edible marine snail; steamed in wine or baked
chiefly trailing poisonous plants with blue flowers
commonly cultivated Old World woody herb having large pinkish to red flowers