**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 friends.