osteoma vs nonmalignant tumour

osteoma and nonmalignant tumour both are nouns.

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

As nouns, nonmalignant tumour is a hypernym of osteoma; that is, nonmalignant tumour is a word with a broader meaning than osteoma:

osteoma: a slow growing benign tumor of consisting of bone tissue; usually on the skull or mandible
nonmalignant tumour: a tumor that is not cancerous

Other hypernyms of osteoma include benign tumor, benign tumour, nonmalignant neoplasm, nonmalignant tumor.

osteoma (noun)	nonmalignant tumour (noun)
a slow growing benign tumor of consisting of bone tissue; usually on the skull or mandible	a tumor that is not cancerous