I seem to be having a lot of trouble understanding when to use 'si' versus another pronoun.

In the following sentence, for example...

Martha and she asked their husbands to wait in the restaurant.
Marta kaj sxi petis, ke _____ edzoj atendu en la restoracio.

My task is to fill in the blank with the correct pronoun. According to "Kurso de Esperanto," "siaj" is wrong and "iliaj" is correct.

But how do we know whose husbands they asked to wait? Their own husbands, or the husbands of some other people? Am I correct in assuming that the two women asked two men who were NOT their own husbands to wait?

And in this example...

The inhabitants ran away because their house burned down.
La logxantoj forkuris, cxar ______ domo brulis.

The correct answer is "ilia," but I don't understand why. In my first example, it cannot be said with certainty if "She" and "Maria" are the wives of the husbands being asked to wait, so that sentence is a little ambiguous. In this sentence, however, it wouldn't make much sense for some other people to run away because some other people's house burned down. The people who owned the house, and were inside of it, would most likely be the ones to run away, so I thought "sia" would be more appropriate, but apparently it is not. Why is that?

And in these two sentences...

The ship sank with her passengers.
Dronis la sxipo kun ____ pasagxeroj.

Esperanto is a very useful langauge; its grammar is regular.
Esperanto estas tre ultila lingvo. ____ gramatiko estas regula.

For the first sentence, the correct answer is "sia," but in the second sentence, the correct answer is "gxia."

Can anyone explain to me the difference between the two sentences, and why one warrants the use of "si," while the other does not?

Thank you

Si is used instead of the normal 3rd person pronouns (li, ŝi, ĝi, ili) when referring to the subject of the sentence:

Paŭlo lavas sin. – Paul washes himself.
Paŭlo lavas lin. – Paul washes him. (It means someone else).

Ili lavas sin. – They wash themselves.
Ili lavas ili. - They wash others.

The reflexive pronoun is not used for the 1st and 2nd person (Mi lavas min. – I wash myself).

More info here

I hope that helps

MrSlippery:Martha and she asked their husbands to wait in the restaurant.
Marta kaj ŝi petis, ke _____ edzoj atendu en la restoracio.

Marta kaj ŝi petis, ke iliaj edzoj atendu en la restoracio.
Marta kaj ŝi petis siajn edzojn atendi en la restoracio.
Marta kun sia amikino petis iliajn edzojn atendi en la restoracio.
Marta kaj ŝia amikino petis siajn edzojn atendi en la restoracio.
Mi kun mia amikino petis niajn edzojn atendi en la restoracio.

MrSlippery:The inhabitants ran away because their house burned down.
La loĝantoj forkuris, cxar ______ domo brulis.

La loĝantoj forkuris, ĉar ilia domo brulis.
La loĝantoj forkuris el sia domo, ĉar ĝi brulis.

MrSlippery:The ship sank with her passengers.
Dronis la ŝipo kun ____ pasaĝeroj.

Dronis la ŝipo kun siaj pasaĝeroj.
Dronis la ŝipo kaj ĝiaj pasaĝeroj.

MrSlippery:Esperanto is a very useful langauge; its grammar is regular.
Esperanto estas tre ultila lingvo. ____ gramatiko estas regula.

Esperanto estas tre ultila lingvo. Ĝia gramatiko estas regula.
Esperanto estas tre ultila lingvo, kies gramatiko estas regula.

Use sia, if it refers to the subject of the sentence or the same part of the complex sentence containing it.
Sia is not used in other part of the complex sentence, divided by ke, ĉar etc. or in the next sentence. Use lia, ŝia, ĝia or ilia. Sia also is not used in the complex subject (la ŝipo kaj ĝiaj pasaĝeroj).
If the subject is mi, ni or vi, use mia, nia and via.

But how do we know whose husbands they asked to wait?

In that case you can't know, but it is reasonable to suppose (without further context) that they aren't the husbands of other women.

A similar ambiguity exists in English. They asked their husbands to wait.

However, through the use of 'sia', Esperanto can often resolve an ambiguity which exists in English. Look at Sergej's examples.

MrSlippery:I seem to be having a lot of trouble understanding when to use 'si' versus another pronoun.

In the following sentence, for example...

Martha and she asked their husbands to wait in the restaurant.
Marta kaj sxi petis, ke _____ edzoj atendu en la restoracio.

My task is to fill in the blank with the correct pronoun. According to "Kurso de Esperanto," "siaj" is wrong and "iliaj" is correct.

But how do we know whose husbands they asked to wait? Their own husbands, or the husbands of some other people? Am I correct in assuming that the two women asked two men who were NOT their own husbands to wait?

And in this example...

The inhabitants ran away because their house burned down.
La logxantoj forkuris, cxar ______ domo brulis.

The correct answer is "ilia," but I don't understand why. In my first example, it cannot be said with certainty if "She" and "Maria" are the wives of the husbands being asked to wait, so that sentence is a little ambiguous. In this sentence, however, it wouldn't make much sense for some other people to run away because some other people's house burned down. The people who owned the house, and were inside of it, would most likely be the ones to run away, so I thought "sia" would be more appropriate, but apparently it is not. Why is that?

And in these two sentences...

The ship sank with her passengers.
Dronis la sxipo kun ____ pasagxeroj.

Esperanto is a very useful langauge; its grammar is regular.
Esperanto estas tre ultila lingvo. ____ gramatiko estas regula.

For the first sentence, the correct answer is "sia," but in the second sentence, the correct answer is "gxia."

Can anyone explain to me the difference between the two sentences, and why one warrants the use of "si," while the other does not?

Thank you

One "trick" to remember is that if the "up in the air" pronoun is in a separate clause (as in thy sentences 1 and 3) which are separated by either a conjunction or a semicolon, then "si" cannot be used.
If there is only one clause (as in 2 and 4), then "si" is used when the possessed object(s) belong(s) to the subject of the sentence.
In thy first sentence, I believe it would generally be understood that the husbands in question are the husbands of Martha and she. If any other meaning is intended (at least in English), then it is made clear, either explicitly by additional verbiage or else implicitly by context.

MrSlippery:
But how do we know whose husbands they asked to wait? Their own husbands, or the husbands of some other people? Am I correct in assuming that the two women asked two men who were NOT their own husbands to wait?

There are not only sia, ŝia, ilia etc., but also (ĉi) ties and (ĉi) tiu. If you speak about husbands of other women, who were mentioned in the previous sentence, speak ties edzoj. If the husbands were mentioned theirselves, use tiuj edzoj. If we don't know who are the wifes, we can speak ies edzoj.

This is alluded to in the other posts, but maybe not clearly stated - "si" and forms of "si" (sia, siaj) can never be the subject of a verb.

So if you have a fill in the blank where you have "blalbalba, ___ [verb] bla bla", and ___ is the subject of [verb] -- that should never ever be filled with a form of "si". Since "si" refers back to the subject of its verb, it can never be the subject, otherwise it has nothing to refer to.

This rule of thumb will help you. Just ask yourself "Is 'si' the subject of a verb here?" and if the answer is "yes", then don't put "si" in that place, since "si" is never a subject.

**How to use the reflexive pronoun "si" and "sia"**

"Si" is a pronoun used only for the third person, which represents the subject of the last action expressed.

Here are some examples of how it is used:

**"La virino rigardis la bildon antaŭ si"**
The woman looked at the picture in front of her.

**"Li eniris sian domon"**
He entered his (own) house.

**"La infano amas sian patrinon"**
The child loves his (own) mother.

**"La viro batis sian hundon"**
The man beat his (own) dog.

Here, "sian" is a reflexive possessive pronoun that refers to the subject of the sentence ("la viro"). It indicates that the dog belongs to the man who is doing the action.

**"La viro batis lian hundon"**
The man beat his dog.

In this case, "lian" is a non-reflexive possessive pronoun and refers to another person (another man, not the subject of the sentence). It indicates that the dog belongs to someone other than the subject of the sentence. It's someone else's dog, another man's.

**Use "si" or "sia" when the following requirements are met:**

1. The pronoun is not part of the subject.
2. The pronoun refers to the subject of the verb.

It is wrong to say "la viro kaj sia edzino estas..." because "lia edzino" is part of the subject. The correct thing would be "la viro kaj lia edzino estas...".

It is important to note that "si" and "sia" are used to refer to the subject of the verb and not the subject of the sentence, because although they are usually the same, they are not always the same. "Si" and "sia" are used when the pronoun refers to the subject of the same clause. "Si" and "sia" represent the subject of the last action expressed before these pronouns, as long as this last action does not belong to a different clause.

**"ŝi vidis lin bati sin"**
She saw him hit himself.

**More examples:**

**"La viro diris, ke lia amiko vidis sian hundon"**
Here, "sian" refers to "lia amiko", which is the subject of the verb "vidis" within the subordinate clause "ke lia amiko vidis sian hundon".

**"La viro diris, ke lia amiko vidis lian hundon."**
Here, "lian hundon" refers to another man's (not friend's) dog.

**"la viro diris, ke lia amiko vidis sian hundon" vs "la viro diris, ke sia amiko vidis sian hundon"**

In Esperanto, when saying "La viro diris, ke lia amiko vidis sian hundon" it is already understood that "lia amiko" is the friend of the "viro" and "sian hundon" refers to the friend's dog. "sia amiko" is not used in this context because "sia" is a reflexive pronoun that refers to the subject of the verb, and in this case the subject is "lia amiko", not "la viro".

**"La viro diris al sia amiko, ke li vidis sian hundon."**

"La viro" = The man.
"diris al sia amiko" = he told his friend.
"sia" refers to the subject of the main clause ("la viro").
"ke li vidis sian hundon" = that he saw his (own) dog.
"sian" refers to the subject of the subordinate clause ("li"), who is the same "viro."
Here, "sia amiko" is correct because "sia" refers to the subject of the verb "diris" ("la viro"). The absence of the comma means that "sia amiko" is part of the direct object of "diris" and reflexively refers to the subject "la viro". In this case, "la viro diras" is in the same clause as "amiko".

**"La viro diris al sia amiko, ke li vidis lian hundon."**

"La viro" = The man.
"diris al sia amiko" = he told his friend.
"sia" refers to the subject of the main clause ("la viro").
"ke li vidis lian hundon" = that he saw his friend's dog.
"lian" refers to the "amiko".

**"Tom kaj liaj amikoj ludas tabulludon."**
Tom and his friends are playing a board game.

**"Jim estas la plej alta el ĉiuj siaj amikoj."**
Jim is the tallest of all his (own) friends.