The indefinite pronouns that are considered singular take a singular verb form, for example: He had one hot dog, another is too much. Is anyone sitting here? (Anyone is sitting...) Yes, someone is...
An indefinate pronoun refers to something that is not definite or specific or exact. Example: I didn't see Alex in the gym, in fact I didn't see anyone. The place was empty.
Indefinite pronouns are used when the person, thing, or amount is not known or is not mentioned in the sentence. Indefinite pronouns allow us to say something without knowing who or what it is or how...