Usage Note
Alguien is invariable and always refers to people ('someone, somebody'), contrasting with algo for things ('something'). It triggers masculine singular agreement on adjectives: alguien inteligente (not alguiena). In negative contexts nadie replaces it: No vino nadie (not No vino alguien).
Examples
"Alguien dejó la puerta abierta."
Natural Translation
Someone left the door open.

Free starter pack
Building your Spanish vocabulary?
Get the 100 most common Spanish words as a free PDF — one email, no spam.
Related Words
Explore Spanish by topic
SpanishNow
6 min read