ignition vs combustion

ignition and combustion both are nouns.

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

As nouns, combustion is a hypernym of ignition; that is, combustion is a word with a broader meaning than ignition:

Other hypernyms of ignition include burning.

ignition (noun)	combustion (noun)
the act of setting something on fire	the act of burning something
the mechanism that ignites the fuel in an internal-combustion engine	a process in which a substance reacts with oxygen to give heat and light
the process of initiating combustion or catching fire	a state of violent disturbance and excitement