Sentar vs. sentar-se
The Portuguese words sentar and sentar-se both revolve around the action of sitting, but they are not interchangeable. The key difference lies in who is performing the action and who is receiving it. One is transitive (acting on someone else) and the other is reflexive (acting on oneself).
Sentar
B1The verb sentar is a transitive verb, meaning it requires a direct object. It translates to to seat or to place someone or something in a sitting position. The subject of the sentence performs the action of sitting on someone or something else.
A mãe sentou a criança na cadeira.
(The mother seated the child in the chair.)
O anfitrião sentou os convidados na mesa principal.
(The host seated the guests at the main table.)
Eu sentei o boneco na prateleira para decorar o quarto.
(I sat the doll on the shelf to decorate the room.)
O professor sentou o aluno novo na frente da sala.
(The teacher seated the new student at the front of the classroom.)
Por favor, senta o teu avô no sofá mais confortável.
(Please, seat your grandfather on the most comfortable sofa.)
Sentar-se
A1The verb sentar-se is a reflexive verb. This is the most common form and is used when the subject performs the action of sitting on themselves. It directly translates to to sit down or to seat oneself. The reflexive pronoun (me, te, se, nos, vos) indicates that the action returns to the subject.
Eu me sentei na cadeira mais próxima.
(I sat down in the nearest chair.)
Sente-se, por favor. A reunião vai começar.
(Sit down, please. The meeting is about to start.)
Eles se sentaram no chão para conversar.
(They sat down on the floor to talk.)
Nós gostamos de nos sentar no parque e ler um livro.
(We like to sit down in the park and read a book.)
Quando a campainha tocou, ela se sentou rapidamente.
(When the bell rang, she sat down quickly.)
Summary
In essence, the difference is straightforward: you use sentar when you are seating someone or something else (e.g., A mãe sentou o bebé). You use sentar-se when you are sitting down yourself (e.g., Eu me sentei). Sentar-se is the correct and much more frequent verb for the act of sitting down.