Indefinite pronouns for people (alguien, nadie)

Someone or No One

When you want to talk about an unknown person or the absence of people, use alguien (someone/anyone) and nadie (no one/nobody/anyone).

Is there anyone in the empty room?
¿Hay alguien en el cuarto vacío?
Someone was crying in the corner.
Alguien estaba llorando en el rincón.

The Double Negative Rule

When a negative word like nadie comes after the verb, you must place no before the verb.

The house was empty; there was nobody.
La casa estaba vacía; no había nadie.

However, if nadie comes before the verb, do not use no.

Nobody knows the secret.
Nadie sabe el secreto.
Nobody left this footprint on the floor.
Nadie dejó esta huella en el piso.

The Personal "A"

Because alguien and nadie refer to people, they require the personal a when they are the direct object of a sentence. If you are seeing, hearing, or looking for "someone" or "no one", use a alguien or a nadie.

I don't see anyone in that dark corner.
No veo a nadie en ese rincón oscuro.
I was looking at the footprints, but I didn't see anyone.
Yo miraba las huellas, pero no vi a nadie.