leaf lettuce vs loose-leaf lettuce

leaf lettuce and loose-leaf lettuce both are nouns.

Word	Noun	Adjective	Verb	Adverb
leaf lettuce	Yes	No	No	No
loose-leaf lettuce	Yes	No	No	No

As nouns, leaf lettuce and loose-leaf lettuce are synonyms defined as:

leaf lettuce and loose-leaf lettuce: lettuce with loosely curled leaves that do not form a compact head

leaf lettuce (noun)	loose-leaf lettuce (noun)
lettuce with loosely curled leaves that do not form a compact head	lettuce with loosely curled leaves that do not form a compact head
distinguished by leaves having curled or incised leaves forming a loose rosette that does not develop into a compact head