Question

What is the part of speech for the word sincerity in this sentence. The sincerity of his answer convinced me.

Answer 1

Sincerity is a noun.

A big clue is the article "the" before it.

Remember, that nouns name persons, places, things, and ideas.

Answer 2

The articles, "the, a, an" are like road signs. The always announce that a noun is ahead. Sometimes there are one or two adjectives between them, but you always know when you see one of those road signs that a noun is coming.