both... depending on how you use it in a sentence!
Metamorphosis is a noun.
No it is a common noun
meta = big
"Metamorphosis" is a common noun. The famous title "The Metamorphosis" authored by Franz Kafka can reasonably be considered a two word proper noun.
The word 'larva' is a noun, a singular, common, concrete noun; a word for an immature form of an insect that will go through a series of changes (metamorphosis) to attain adulthood. The word 'larva' is a word for a thing.
It's a noun. Adjectives are used to describe nouns ("my, you're looking very metamorphosis today" doesn't work, for example).
The word 'noun' is not a verb. The word 'noun' is a noun, a word for a thing.
No, it is a verb or a noun (to go around, to surround; a round shape). The adjective form is circular.
The noun 'is' is a verb, a form of the verb 'to be'. The verb 'is' functions as an auxiliary verb and a linking verb.
noun
A roar is a noun. To roar is a verb.
Training is a noun and a verb. Noun: e.g. activity of acquiring skills. Verb: present participle of the verb 'train'.