osteoma vs nonmalignant tumor

osteoma and nonmalignant tumor both are nouns.

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

As nouns, nonmalignant tumor is a hypernym of osteoma; that is, nonmalignant tumor 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 tumor: a tumor that is not cancerous

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

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