What is the difference between ser and estar in Portuguese?
Ser states what something is — identity, origin, profession, inherent quality. Estar states what condition it is in, or where. The permanent-versus-temporary rule taught in most courses fails often enough to be misleading: identity against condition is the distinction that holds.
Identity against condition
Ser answers what is this; estar answers how or where is this. Ser covers who you are, where you are from, what you do and what you are made of. Estar covers location, mood, health and the result of a change.
Ele é médico.
He is a doctor.
Identity.
Ele está doente.
He is ill.
Condition.
Sou do Brasil.
I'm from Brazil.
Origin — ser.
Estou em casa.
I'm at home.
Location — estar.
Adjectives that change meaning
As in Spanish, a set of adjectives means something different with each verb. With ser you get the inherent quality; with estar the current state or the impression it makes.
É chato / Está chato
He is boring / This is being annoying
É bonita / Está bonita
She is pretty / She looks pretty today
É verde / Está verde
It is green / It is unripe
Where Portuguese differs from Spanish
The broad split matches Spanish closely, but the details do not always transfer. Portuguese uses ficar heavily for becoming and for some states where Spanish would use estar, and a few fixed expressions differ outright.
Fiquei feliz.
I became happy / I was happy about it.
Ficar, where Spanish might use ponerse.
Onde fica o banco?
Where is the bank?
Permanent location often takes ficar.
Common mistakes
Sou cansado.
Estou cansado.
Tiredness is a condition. Sou cansado says being tiresome is part of your character.
Estou brasileiro.
Sou brasileiro.
Nationality is identity rather than a state you are currently in, so it takes ser — regardless of how recently you acquired it or how long you intend to keep it.
Onde está o banco?
Onde fica o banco?
Grammatical, but for a building's permanent location Portuguese prefers ficar.
Frequently asked questions
Is it the same as Spanish ser and estar?
Broadly yes, and the intuition transfers well. The differences are in the edges — ficar takes over some ground that estar covers in Spanish, and a handful of set expressions do not match.
What does ficar actually mean?
To stay, to become, and to be located. It is one of the most useful verbs in Portuguese and has no single Spanish equivalent, which is why Spanish speakers under-use it.
Does this differ between Brazil and Portugal?
The core rules are shared. Some fixed expressions and preferences differ, but nothing that would make you misunderstood.