grammar.pronouns.indefinite
Indefinites: alguien, nadie, algo, nada, alguno, ninguno
Affirmative alguien/algo/alguno pair with negative nadie/nada/ninguno. After the verb, negatives require no before it: no vino nadie.
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Explanation
Indefinite pronouns talk about unspecified people and things, in matched affirmative/negative pairs. People: alguien ('someone') / nadie ('no one'). Things: algo ('something') / nada ('nothing'). With a following noun, use alguno / ninguno, which agree and shorten to algún / ningún before a masculine singular noun: algún día, ningún problema.
Spanish requires double negation when the negative word comes after the verb: no vino nadie, no hay nada, no tengo ninguna duda. If you front the negative before the verb, the no disappears: nadie vino, nada importa.
A few quirks: ninguno is almost always singular (ningún problema, not *ningunos problemas), and algo/nada can modify adjectives adverbially, algo caro ('somewhat expensive'), nada fácil ('not easy at all'). Alguien and nadie are invariable (no gender or number).
Examples
Does anyone have change?
Region: global
There's no problem at all.
Region: global
Is there anything to eat?, No, there's nothing left.