Mais tarde vs. depois
While both mais tarde and depois can be translated as "later" or "after" in English, they are not always interchangeable. The key difference lies in what they emphasize: mais tarde emphasizes a later point in time, while depois emphasizes the sequence of events.
Mais tarde
A1This phrase literally translates to "more late" and is used to refer to a later point in time, usually within the same day or in the near future. It answers the question "When?". It focuses on the passage of time before an action occurs.
Agora estou ocupado, ligo para você mais tarde.
(I'm busy now, I'll call you later.)
Podemos terminar a reunião mais tarde?
(Can we finish the meeting later?)
Ele prometeu que chegaria, mas apareceu muito mais tarde.
(He promised he would arrive, but he showed up much later.)
Vou ao supermercado mais tarde, depois do trabalho.
(I'm going to the supermarket later, after work.)
Ela decidiu deixar a tarefa para mais tarde.
(She decided to leave the task for later.)
Depois
A1This word means "afterwards" or "then" and is primarily used to show the order of events in a sequence. It answers the question "What happens next?". It can be used alone or in constructions like depois de (after + noun) or depois que (after + action).
Primeiro, vamos jantar e depois vamos ao cinema.
(First, let's have dinner and afterwards we'll go to the movies.)
O que você vai fazer depois da aula?
(What are you going to do after class?)
Eu só vou dormir depois que você chegar em casa.
(I will only go to sleep after you get home.)
Ele lavou a louça e, depois, limpou o chão.
(He washed the dishes and, then, cleaned the floor.)
Eles se conheceram na faculdade e se casaram anos depois.
(They met in college and got married years later.)
Summary
In essence, use mais tarde when you are talking about an unspecified, later point in time (answering "when?"). Use depois when you are talking about the order of events or what comes next in a sequence (answering "what's next?"). While depois can sometimes mean "later", its core function relates to sequence, which is why it is often followed by de or que to link it to another event.