Identify the italicized word according to its class in structural linguistics.

Rain began to fall.

intensive

adjective

noun

empty word

verb

I don't know which word is underlined, so I will just write every part of speech.

Rain is a noun.

Began is a linking verb.

To is an empty word.

Fall is a verb.

Or to fall could be seen as a verb, you don't have to separate them.

But again, you didn't underline anything, so I don't know for sure.