sweet-birch oil vs birch oil

sweet-birch oil and birch oil both are nouns.

Word	Noun	Adjective	Verb	Adverb
sweet-birch oil	Yes	No	No	No
birch oil	Yes	No	No	No

As nouns, sweet-birch oil and birch oil are synonyms defined as:

sweet-birch oil and birch oil: a liquid ester with a strong odor of wintergreen; applied externally for minor muscle and joint pain

Other synonyms of sweet-birch oil include methyl salicylate.

sweet-birch oil (noun)	birch oil (noun)
a liquid ester with a strong odor of wintergreen; applied externally for minor muscle and joint pain	a liquid ester with a strong odor of wintergreen; applied externally for minor muscle and joint pain