lemongrass oil vs lemongrass

lemongrass oil and lemongrass both are nouns.

Word	Noun	Adjective	Verb	Adverb
lemongrass oil	Yes	No	No	No
lemongrass	Yes	No	No	No

As nouns, lemongrass oil and lemongrass are synonyms defined as:

lemongrass oil and lemongrass: an aromatic oil that smells like lemon and is widely used in Asian cooking and in perfumes and medicines

Other synonyms of lemongrass oil include lemon grass.

lemongrass oil (noun)	lemongrass (noun)
an aromatic oil that smells like lemon and is widely used in Asian cooking and in perfumes and medicines	a tropical grass native to India and Sri Lanka
	an aromatic oil that smells like lemon and is widely used in Asian cooking and in perfumes and medicines