romaine vs cos lettuce

romaine and cos lettuce both are nouns.

Word	Noun	Adjective	Verb	Adverb
romaine	Yes	No	No	No
cos lettuce	Yes	No	No	No

As nouns, romaine and cos lettuce are synonyms defined as:

romaine and cos lettuce: lettuce with long dark-green leaves in a loosely packed elongated head

Other synonyms of romaine include cos, romaine lettuce.

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