combustion vs flame

combustion and flame both are nouns.

Word	Noun	Adjective	Verb	Adverb
combustion	Yes	No	No	No
flame	Yes	No	Yes	No

As nouns, flame is a hyponym of combustion; that is, flame is a word with a more specific, narrower meaning than combustion:

combustion: a process in which a substance reacts with oxygen to give heat and light
flame: the process of combustion of inflammable materials producing heat and light and (often) smoke

Other hyponyms of combustion include deflagration, fire, flaming, internal combustion.

combustion (noun)	flame (noun)
the act of burning something	the process of combustion of inflammable materials producing heat and light and (often) smoke
a process in which a substance reacts with oxygen to give heat and light
a state of violent disturbance and excitement

combustion (verb)	flame (verb)
	criticize harshly, usually via an electronic medium
	be in flames or aflame
	shine with a sudden light