aroma vs odour

aroma and odour both are nouns.

Word	Noun	Adjective	Verb	Adverb
aroma	Yes	No	No	No
odour	Yes	No	No	No

As nouns, aroma and odour are synonyms defined as:

Other synonyms of aroma include odor, olfactory property, scent, smell.

As nouns, odour is a hypernym of aroma; that is, odour is a word with a broader meaning than aroma:

aroma: a distinctive odor that is pleasant
odour: the sensation that results when olfactory receptors in the nose are stimulated by particular chemicals in gaseous form

Other hypernyms of aroma include odor, olfactory perception, olfactory sensation, smell.

aroma (noun)	odour (noun)
any property detected by the olfactory system	any property detected by the olfactory system
a distinctive odor that is pleasant	the sensation that results when olfactory receptors in the nose are stimulated by particular chemicals in gaseous form