James brushes his teeth two times a day.

In the given sentence, James and teeth are the nouns.

As the word teeth is the plural form of tooth and it doesn’t usually end with -s; it is an irregular plural noun.

Police arrested three thieves last night.

In the given sentence, Police and thieves are the nouns.

As the word thieves is the plural form of thief and it doesn’t usually end with -s; but it ends with -ves; So it is an irregular plural noun.

We need three dice to play this game.

In the given sentence, dice is the noun.

As the word dice is the plural form of die and it doesn’t usually end with -s; it is an irregular plural noun.