Algún, ningún, algo and alguien are all indefinite pronouns. Learn about indefinite pronouns in Spanish with BBC Bitesize Spanish. For students between the ages of 14 and 16.

Indefinite articles are used to mark nouns that have not been mentioned before, or that the listener or reader does not know anything about.

IT'S very well-established in English grammar that (1) the verb must always agree with the number — singular or plural — of the noun or pronoun that does or states the action, and that (2) the pronoun ...

The indefinite pronouns algún and ningún need to agree in gender (when possible) and in number with the noun they are substituting. Algo and alguien are not gender or number specific. algún ...