Lactuca sativa longifolia vs romaine lettuce

Lactuca sativa longifolia and romaine lettuce both are nouns.

Word	Noun	Adjective	Verb	Adverb
Lactuca sativa longifolia	Yes	No	No	No
romaine lettuce	Yes	No	No	No

As nouns, Lactuca sativa longifolia and romaine lettuce are synonyms defined as:

Lactuca sativa longifolia and romaine lettuce: lettuce with long dark-green spoon-shaped leaves

Other synonyms of Lactuca sativa longifolia include cos lettuce.

Lactuca sativa longifolia (noun)	romaine lettuce (noun)
lettuce with long dark-green spoon-shaped leaves	lettuce with long dark-green leaves in a loosely packed elongated head
	lettuce with long dark-green spoon-shaped leaves