smell vs odour

smell and odour both are nouns.

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

As nouns, smell and odour are synonyms defined as:

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

As nouns, smell and odour are synonyms defined as:

smell and odour: the sensation that results when olfactory receptors in the nose are stimulated by particular chemicals in gaseous form

Other synonyms of smell include odor, olfactory perception, olfactory sensation.

smell (noun)	odour (noun)
the act of perceiving the odor of something	any property detected by the olfactory system
any property detected by the olfactory system	the sensation that results when olfactory receptors in the nose are stimulated by particular chemicals in gaseous form
the faculty that enables us to distinguish scents
the sensation that results when olfactory receptors in the nose are stimulated by particular chemicals in gaseous form
the general atmosphere of a place or situation and the effect that it has on people

smell (verb)	odour (verb)
become aware of not through the senses but instinctively
emit an odor
inhale the odor of; perceive by the olfactory sense
smell bad
have an element suggestive (of something)