When to use Ser vs. Estar

To be permanently or not to be permanently

Use "ser" when...

Talking about the essence of something
Use "ser" when you want to talk about the essence of something.  Meaning, who and what it is.

A good general rule of thumb is to use "ser" whenever you are also using the words: who, what, and when

  • Camila es inteligente.
    Camila is intelligent
  • Nosotros somos de Nueva York.
    We are from New York.
  • Mateo es muy alto.
    Mateo is very tall.
  • Nosotros somos primos.
    We are cousins.
  • Es un libro
    It is a book

Camila is smart. Not just today, but all of the time. So we use ser, because we're talking about who she is on a permanent basis.

In the same way, we are always going to be from New York, Mateo is going to continue to be tall, and I'll always be cousins with my cousin.  So in all of these cases you would use ser

Using the passive voice
"Ser" is also used in sentences in the passive voice.  Here's the grammatical construction:

Ser + Past Participle + Por 

  • El libro fue escrito por JK Rowling.
    The book was written by JK Rowling.

Expressing emphasis

  • Es el domingo cuando vamos a viajar.
    Sunday is when we are going to travel.

Use "estar" when

Expressing how you feel and where it is...
Use "estar" when you're trying to express how someone feels or where something is.  How and Where are the two words you're keeping a lookout for.

  • Camila está enferma.
    Camila is ill.
  • Mateo está en su casa.
    Mateo is in his house
  • Yo estoy en España hoy.
    I am in Spain today.  (Meaning, at this current moment)

Describing location
Locations always use estar.  Even when the location is fixed, you always use estar.

  • Chicago está en Illinois.
    Chicago is in Illinois.
  • Mi amiga está en la oficina
    My friend is in the office

Discussing appearance
A good way to see the distinction is to pay another visit to Camila.  This time we're going to discuss her appearance.

  • Camila es muy bonita.
    Camila is very pretty. (It's a permanent characteristic.)
  • Camila está bonita esta noche.
  • Camila is pretty tonight. (Because she is dressed up for the party)

In these grammatical constructions, you always use "estar:"

Creating the present continuous tense

  • Estoy aprendiendo español.
    I am leaning Spanish.

Creating the past participle tense

  • Mi reloj está roto.
    My watch is broken.