nonmalignant tumour vs nonmalignant tumor

nonmalignant tumour and nonmalignant tumor both are nouns.

Word	Noun	Adjective	Verb	Adverb
nonmalignant tumour	Yes	No	No	No
nonmalignant tumor	Yes	No	No	No

As nouns, nonmalignant tumour and nonmalignant tumor are synonyms defined as:

nonmalignant tumour and nonmalignant tumor: a tumor that is not cancerous

Other synonyms of nonmalignant tumour include benign tumor, benign tumour, nonmalignant neoplasm.

nonmalignant tumour (noun)	nonmalignant tumor (noun)
a tumor that is not cancerous	a tumor that is not cancerous