Español — Defining vs non-defining relative clauses
In Spanish a relative clause can restrict the noun it modifies (especificativa, no commas) or merely add extra information about it (explicativa, between commas). Compare Los alumnos que estudian aprobarán with Los alumnos, que estudian, aprobarán: only one comma changes who passes.
How it works
The especificativa carries no commas and narrows the reference, singling out a subset: in Los coches que son eléctricos no contaminan, only the electric cars are meant. The explicativa is set off by commas and applies to the whole, already-identified noun as a parenthetical: Los coches, que son eléctricos, no contaminan implies that all the cars are electric. With people, que serves both clause types, but the explicativa readily admits el cual / la cual and, after a comma, quien: Mi hermano, quien vive en Lima, llega hoy.
Examples
| Sentence | Type and what it means |
|---|---|
| Los alumnos que estudian aprobarán. | Especificativa: only the students who study will pass, not the others. |
| Los alumnos, que estudian, aprobarán. | Explicativa: all the students will pass, and by the way they all study. |
| El vecino que tiene perro madrugó. | Especificativa: identifies which neighbour — the one who has a dog. |
| El vecino, que tiene perro, madrugó. | Explicativa: the neighbour is already known; owning a dog is a side note. |
| Mi hermano, quien vive en Lima, llega hoy. | Explicativa with quien: valid only between commas, since I have one brother. |
Good to know
Subject/object quien cannot start a especificativa: say los niños que juegan, not *los niños quienes juegan; quien fits the explicativa (Los niños, quienes ya cenaron, se acostaron). Also, a proper noun or a unique referent is inherently identified, so it normally takes an explicativa: Madrid, que es la capital, ... — not *Madrid que es la capital.