malodor vs odour

malodor and odour both are nouns.

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

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

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

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

malodor (noun)	odour (noun)
a distinctive odor that is offensively unpleasant	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