Accidental se and the middle voice

What it is

When something goes wrong without anyone meaning it to, Spanish likes to make the thing the subject and the person a bystander: Se me cayó el vaso (literally "the glass fell on me"), Se nos acabó la leche, Se le olvidaron las llaves. This is the accidental se (se involuntario or se accidental). It tells your listener that the event happened to you rather than being something you did on purpose.

The same se without a person is the middle voice (voz media): Se abrió la puerta, Se apagó la luz. Something changes on its own, with no agent in sight.

How it works

The pattern has four parts, always in this order: se + indirect pronoun + verb + thing. The indirect pronoun (me, te, le, nos, les) names the person affected. The thing is the grammatical subject, so the verb agrees with it, not with the person: Se me cayó el vaso, but Se me cayeron los vasos.

Four details:

• Se always comes first. ✗ Me se cayó is a very common slip, even among native children; the only order is se me.
• With an infinitive, the verb stays singular: Se me olvidó comprar pan (not ✗ se me olvidaron comprar).
• You can add a + person for clarity or emphasis: A Diego se le perdió el pasaporte. A mí se me olvida todo.
• It works in every tense: Siempre se me olvida (present), Se te va a caer (ir a), Que no se te olvide (subjunctive).

When to use it

Use it for unplanned events, slips and small accidents. The most frequent verbs:

The responsibility contrast is the heart of it. Rompí el vaso means you broke it: maybe on purpose, certainly your doing. Se me rompió el vaso says it broke while you were holding it. Both are correct; the second sounds like an apology built into the grammar, which is why people use it so much when they say sorry.

For the middle voice, drop the person: Se cerró la puerta (the door closed), Se apagaron las luces, Se descompuso la lavadora. Compare the transitive Cerré la puerta (I closed it).

• Se me cayó el vaso cuando sonó el timbre.I dropped the glass when the doorbell rang.accidental
• Rompí el vaso a propósito.I broke the glass on purpose.responsible
• A mí siempre se me olvidan las fechas.I always forget dates.a + person, plural thing
• Se rompió una cuerda de la guitarra en pleno concierto.A guitar string broke in the middle of the concert.middle voice

Contrasts and traps

• ✗ Me se olvidó → Se me olvidó.
• ✗ Se me olvidó las llaves → Se me olvidaron las llaves: the verb agrees with las llaves.
• Pronoun for the person, verb for the thing. A mis tíos se les perdió el perro: les for the uncles (plural), perdió for the dog (singular).
• Without se, the meaning changes. Me olvidó = he forgot me. Me caí = I fell. Se me cayó = I dropped it.
• Olvidar has three patterns: Olvidé el paraguas, Me olvidé del paraguas, Se me olvidó el paraguas. In speech Me olvidé el paraguas (without de) is very common in many regions; the standard forms are the three above.
• Regional verbs for machines that break down: for example se descompuso (Mexico, Central America, Chile), se dañó (Colombia, Venezuela, Ecuador), se malogró (Peru), se rompió (Argentina, Uruguay); Spain says se estropeó. For glass and bones, much of Latin America says quebrar: se me quebró el vaso.

If you speak Portuguese

Portuguese puts the person first: esqueci as chaves, deixei cair o copo, quebrei o prato. Spanish can say olvidé las llaves or rompí el plato too, but for accidents se me olvidaron las llaves, se me cayó el vaso and se me rompió el plato sound far more natural. Brazilian me esqueci (de) becomes se me olvidó (no de) or me olvidé de. And where Portuguese says a porta abriu or a luz apagou, Spanish needs se: se abrió la puerta, se apagó la luz.