I'm trying to undertstand this sentence:
Se me olvidaron las llaves.
I can roughly figure out the meaning of "I forgot the keys, but I can't understand the usage of "se me olvidaron".
What's the usage of se me olvidaron?
Is the usage the same as this?
Se lo dice/dicen que ... (It is said that ...)
I found this:
The verb "olvidar" (to forget) has many ways :
1- Transitiv Verb:
Yo olvidé la cartera en casa. (I forgot the purse at home)
The subject yo (I) is the one that olvida (forgot), direct complement la cartera (the purse), is the thing olvidado (forgotten).2- Pronominal Intransitiv Verb (olvidarse) (forget)
Se me olvidó la cartera en casa. (I forgot the purse at home (no translation))
The subject la cartera (the purse) is what has been olvidado (forgotten), the indirect complement me (yo) (I) is the one who forgets; se is a part of the verb and has no grammatical function.3- Pronominal Intransitiv Verb + de (of/to):
Yo me olvidé de traer la cartera. (I forgot to bring the purse)
The subject yo (I) is the one that forgets, the forgotten thing is presented by de (of/to); me (I) is a part of the verb and has no grammatical function.
Take a look at the conjugations for Olvidar and Olvidarse (In example: yo me olvido (I forget (myself)), tu te olvidas (Thou/you forget (thy/your self)), él se olvida (he forget (himself)), nos. nos olvidamos (we forget (ourselves)), vos. os olvidáis (you forget (yourself)), ellos se olvidan (they forget (themselves)))
Info with all the possible uses fo "SE": RAE
Encontré esto:
El verbo "olvidar" admite varias construcciones:
1- Verbo Transitivo:
Yo olvidé la cartera en casa.
El sujeto yo es quien olvida, objeto directo la cartera, es lo olvidado.2- Verbo Intransitivo Pronominal (olvidarse)
Se me olvidó la cartera en casa.
El sujeto la cartera es lo olvidado, el objeto indirecto me (yo) es quien olvida; se forma parte del verbo y no tiene función gramatical.3- Verbo Intransitivo Pronominal + de:
Yo me olvidé de traer la cartera.
El sujeto yo es quien olvida, lo olvidado viene introducido por de; me forma parte del verbo y no tiene función gramatical.
Ver conjugaciones de Olvidar y Olvidarse (por ejemplo: yo me olvido, tu te olvidas, él se olvida, nos. nos olvidamos, vos. os olvidáis, ellos se olvidan)
Info con todos los usos de SE: RAE
Athough this source confirms, in its first part, what Billeeb said in his answer, I am more inclined to believe -- as can be seen in the last part of the same source I just quoted -- that in "se me olvidaron las llaves" the particle "se" denotes a passive meaning, so "olvidaron" is actually transitive.
Manuel Seco says that: (1) "olvidar" can be transitive ("olvidar algo") or pronominal and intransitive, in which case it takes the preposition "de" ("olvidarse de algo") -- we also have the transitive "olvidarse algo", where the particle "se" has emotional value, so to speak; (2) "olvidársele (a alguien) algo" is passive and transitive, with "algo" being the subject of the passive and the forgetful person being the indirect object:
1. Construcción: olvidé el paraguas; olvidé hacerlo; olvidé que era fiesta; me olvidé del paraguas, me olvidé de hacerlo; me olvidé de que era fiesta.
En la forma pronominal (olvidarse), no debe omitirse la preposición "de" en la lengua escrita o formal: "Me olvidé que tenía invitados", por "Me olvidé de que tenía invitados". Sin embargo, esta omisión se acepta en la lengua hablada, y por otra parte no son raros los ejemplos en la literatura.
2. Al lado de los casos a que se refiere el apartado anterior, en que el verbo es activo y su sujeto es de persona, hay otras construcciones en que el verbo es pronominal pasivo (o “pasivo reflejo”) y tiene un sujeto que designa la cosa olvidada. En estas construcciones hay un pronombre personal complemento de interés, que representa a la persona olvidadiza: Se nos olvidaron las fotos; Se le olvidó hacerlo; No se os olvide que mañana es fiesta. Se distinguen estas construcciones por la presencia del pronombre "se" seguido de otro pronombre personal átono (me, te, le, nos, os, les), y por el verbo siempre en tercera persona en concordancia singular o plural con la cosa olvidada.
My claim that "se me olvidaron las llaves" is passive transitive is based on the fact that in other similar constructions the verb will be clearly intransitive, for example:
Instead, in:
we have: Las llaves fueron olvidadas (which is clearly passive: The keys were left behind).
In Spanish, you could say this sentence in two ways.
Olvidé las llaves.
Se me olvidaron las llaves.
In the first case, you are the subject of the sentence. It could be because you purposely forgot them or because you accidentally forgot them, but you forgot the keys.
In the second sentence, however, the subject is the keys being lost. You are the one being affected by the accident. In this sentence, the se is an accidental se, showing that without a doubt, it was an accident. That you didn't mean to forget the keys. "Se me olvidaron las llaves" basically translates to "The keys were forgotten to me."
I agree with @gustavson but will write a simpler answer for anyone who might benefit.
Let's say we are just coming home from visiting Aunt Leticia who lives an hour away. We discover we are without house keys because they got left behind at Aunt Leticia's house. Let's write a passive sentence:
Las llaves se olvidaron allá, en casa de mi Tía Leticia.
Now we get to be a bit picturesque because Spanish allows us to do this, and we will add an indirect object that shows whom this terrible thing happened to:
Las llaves se nos olvidaron en casa de mi Tía Leticia.
A common variant of this is
Las llaves se nos quedaron en casa de mi Tía Leticia. | The keys got left behind at Aunt Leticia's house [and that affected US].
The implication is that we are the dummies that made the boo-boo, or the poor idiots who had the bad luck.
As Gustavson pointed out, this construction is similar to
Se me cayó el lápiz. | The pencil fell [which affected ME].
Here's a similar construction in English:
And then she up and died on me.
Although this has some differences from the llaves construction, it's a nice example of how the person affected can show up in a picturesque expression.
Turning now to your Question 2:
Is the usage the same as this?
Se lo dice/dicen que ... (It is said that ...)
It would be the same, I guess, except that "Se lo dice" doesn't work. "It is said" would be expressed in Spanish as
Se dice que ...
