arc vs rainbow

arc and rainbow both are nouns.

Word	Noun	Adjective	Verb	Adverb
arc	Yes	No	Yes	No
rainbow	Yes	No	No	No

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

arc: something curved in shape
rainbow: an arc of colored light in the sky caused by refraction of the sun's rays by rain

arc (noun)	rainbow (noun)
electrical conduction through a gas in an applied electric field	an illusory hope
a continuous portion of a circle	an arc of colored light in the sky caused by refraction of the sun's rays by rain
something curved in shape

arc (verb)	rainbow (verb)
form an arch or curve