combustion vs arson

combustion and arson both are nouns.

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

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

Other hyponyms of combustion include fire-raising, incendiarism, firing, ignition, inflammation, kindling, lighting, incineration.

combustion (noun)	arson (noun)
the act of burning something	malicious burning to destroy property
a process in which a substance reacts with oxygen to give heat and light
a state of violent disturbance and excitement