Something or Nothing
To talk about unspecified things, use algo (something) and its negative counterpart nada (nothing).
| I hear something strange in the street. | Oigo algo raro en la calle. |
Notice how Spanish handles negative sentences. If nada comes after the verb, you must place no before the verb. While this sounds like a "double negative" in English (literally "I don't hear nothing"), it is completely natural—and required—in Spanish!
| I don't hear anything, the street is empty. | No oigo nada, la calle está vacía. |
| The party is boring, nothing is happening. | La fiesta es aburrida, no ocurre nada. |
Someone or No One
When talking about unspecified people, use alguien (someone) and nadie (no one).
| But there is no one, it is just a voice. | Pero no hay nadie, es solo una voz. |
The same double negative rule applies to nadie. If it comes after the verb, you need a no before the verb. However, if nadie is the subject and comes before the verb, you do not use no.
| No one forgets a good friend. | Nadie olvida a un buen amigo. |
The Personal "A"
Remember that alguien and nadie always refer to people. Because of this, when they are the direct object of a sentence (meaning they are the person receiving the action of the verb), they must be preceded by the personal a.
| Do you hear anyone? I hear a voice. | ¿Oyes a alguien? Oigo una voz. |
| The girl doesn't see anyone in the street. | La niña no ve a nadie en la calle. |
