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 ...

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 ...

Collective nouns such as "them" take the singular if they are acting as a unit and the plural if they are acting as individuals. Ex: The team (as individuals) decide today if they want to strike. The ...