These are situations where the agent does not claim responsibility for something that happened (caer, olvidar, perder, quedar, romper, quemar…)
(Clarifying phrase) +Se + indirect object pronoun + verb + subject always begin with se (constant) IDOP tells you who the action happened to Verb is always Ud. or Uds. and agrees with how many things were involved (subject)
Are for emphasis A mí A ti A él/ella/Ud. A nosotros A ellos/ellas/Uds.
Se + IOP Se is constant in formula, IOP is variable and explains to whom the unintentional event happened. Se me Se te Se le Se nos Se les
Caer = to drop Quemar = to burn Olvidar = to forget Acabar = to run out Quedar = to leave behind Perder = to lose Romper = to break Descomponer = to break down/stop working
Se me olvidaron las llaves. I forgot the keys (unintentionally). Se le cayó la torta. He dropped the cake (accidentally).
Ella rompió el vaso. (Active Construction) She broke the glass. Se le rompió el vaso. (SE construction) She broke the glass (accidentally).
The verb used agrees with the subject (the thing or things) and will be singular (Ud.) or plural (Uds.) Typically the preterite is used with this construction Se me cayó el libro. Se me cayeron los libros.
The tourist lost his passport. I forgot my wallet. You left your homework at home. We dropped the plates. Their car broke down.
Al turista se le perdió el pasaporte. Se me olvidó la cartera/billetera. Se te quedó la tarea en casa. Se nos cayeron los platos. Se les descompuso el carro.