Ser or estar? The two Spanish “to be”
Ser says what someone or something is. Estar says how or where it is right now.
Use ser for identity: name (Soy Ana), origin (Soy de México), job (Es médica), time (Son las tres). Use estar for states and location: feelings (Estoy cansado), place (Estoy en casa), actions in progress (Está comiendo), temporary states (Está cerrado). Watch out: the place of an event takes ser — La fiesta es en mi casa.
Some adjectives change meaning: es aburrido = he is boring, está aburrido = he is bored; es listo = he is clever, está listo = he is ready.
Examples
Soy alérgico al marisco.
I'm allergic to shellfish.
Estoy de camino.
I'm on my way.
Mi hermana es profesora.
My sister is a teacher.
¿Dónde está el baño?
Where is the bathroom?
La paella está muy rica.
The paella is delicious.
La fiesta es en mi casa.
The party is at my place.
Common mistake
Wrong: Soy cansado. Right: Estoy cansado (I'm tired) — a feeling is a state, so estar. Wrong: Está profesora. Right: Es profesora (She's a teacher) — a job is identity, so ser.