Si and Sia: The Esperanto Reflexive, and the English Ambiguity It Fixes

Read this English sentence and tell me whose dog it is.

He saw his dog.

You cannot. Nobody can. English gives you his and leaves you to guess whether the dog belongs to the man doing the seeing or to some other man mentioned two sentences earlier. Native speakers patch it with his own or by repeating a name, and mostly do not notice how often the patch is needed.

Esperanto has a word for it.

Li vidis sian hundon. - He saw his own dog.

Li vidis lian hundon. - He saw the other man's dog.

That is the whole point of si and sia, and it is worth the twenty minutes it takes to get right.

The forms

Si is the reflexive pronoun. Sia is its possessive adjective. Both behave exactly as you would expect from the rest of the language.

The -n is the ordinary accusative from the -n article, and sia agrees for number and case like any adjective. There is nothing new to learn about the endings.

The starred rows are marked because they are almost always wrong, for a reason we get to in a moment.

Third person only

Si exists only for li, ŝi, ĝi, ili and oni. There is no reflexive mi or vi, and this is not an oversight.

A sentence with mi in it cannot have a second, different mi to confuse it with, so min is already unambiguous and no special form is needed. The third person is the only place where genuine confusion is possible, so it is the only place Esperanto spends a word.

The rule that catches everyone: si is never the subject

One line, and it explains most of the mistakes people make.

Si points back at a subject, so it cannot be one. By extension, sia cannot sit inside a subject phrase either.

Wrong: Sia patro amas lin.

Right: Lia patro amas lin. - His father loves him.

The father is the subject, so anything describing him has to be lia, referring back to the lin later in the sentence. Sia there would be pointing at the subject from inside the subject, which is a snake eating its own tail.

The same applies to compound subjects, and this one trips up people who have otherwise got it:

Wrong: Li kaj sia frato venis.

Right: Li kaj lia frato venis. - He and his brother came.

Both li and frato are subjects. Nothing there can be sia.

This is why those two starred rows in the table above are marked. Sia hundo estas granda is a sentence looking for an antecedent it will never find.

Inside a subordinate clause

Si refers to the subject of its own clause, not of the sentence as a whole. This is the second-order rule, and once you have it you can parse anything.

Li diris, ke ŝi prenis sian ĉapelon. - He said she took her own hat.

Li diris, ke lia frato venos. - He said his brother would come.

In the first, the ke clause has ŝi as its subject, so sian is hers. In the second, the ke clause's subject is lia frato - and since sia cannot live inside a subject, it must be lia, which then reaches back to the li of the main clause. The two rules do the work between them without you needing a third.

Li petis, ke mi helpu lin. - He asked me to help him.

Here the clause's subject is mi, and mi does not use si at all, so the object has to be lin, meaning the asker.

The corner that is genuinely disputed

Infinitives have no subject of their own, so the "subject of its own clause" rule has nothing to grip.

Li petis la knabon helpi sin.

Whom does the boy help? Practice generally follows the doer of the infinitive, which makes this he asked the boy to help himself. That is the reading I would defend, and the one most careful writers intend. But I am not going to pretend it is settled, because it is not: you will find published Esperanto going the other way, and readers who parse it the other way.

The right answer is to not write the sentence. Turn it into a ke clause, where the rules are unambiguous:

Li petis, ke la knabo helpu sin. - Help himself, the boy.

Li petis, ke la knabo helpu lin. - Help him, the asker.

Any construction whose meaning depends on a disputed rule is a bad construction, however defensible your side of the dispute is.

Ili: themselves or each other?

Sin with a plural subject is ambiguous in a way the singular never is.

Ili amas sin.

That is they love themselves or they love each other, and Esperanto's reflexive does not distinguish them. Context usually does. When it does not, the reciprocal has its own phrase:

Ili amas unu la alian. - They love each other.

Unu never changes; alia takes the accusative because it is the object. If the reciprocal relation involves a preposition, unu stays put and the preposition goes in the middle: ili parolis unu kun la alia, they spoke with one another.

Si mem for emphasis

Mem means self in the emphatic sense, and it stacks onto the reflexive when you want to underline that the subject really did it to itself:

Li vidis sin mem. - He saw his very self.

Li mem faris tion. - He did it himself.

Note the difference. Sin mem is an emphatic object; li mem is an emphatic subject, and has nothing to do with the reflexive at all. Learners collapse the two constantly.

Propra (own) does a related job for possession: sia propra domo is his very own house, doubling down on what sia already says. Use it for stress, not as a crutch.

Reach for -iĝ- before you reach for sin

If you come from French, Spanish or Italian, your instinct will be to build reflexive verbs. Resist it. Esperanto has -iĝ- for exactly this, and the -ig- and -iĝ- article covers the machinery.

La pordo malfermiĝis is the door opened. La pordo malfermis sin claims the door performed an act of self-opening, which is not what anybody means. Keep sin for the cases where the subject genuinely acts on itself, and there the reflexive is exactly right: li defendis sin, li kaŝis sin post la arbo.

Where sin has frozen into words

A handful of common words carry sin inside them, with the accusative already baked in because it was the object of the verb the word is built from:

You can read every one of them off the parts, which is the usual Esperanto bargain. And because affixes are productive, you can build more when you need them.

What to take away

• sia = the subject's own; lia / ŝia / ilia = somebody else's.
• si takes -n (sin); sia agrees like any adjective (sian, siaj, siajn).
• Third person only. Mi and vi need nothing.
• Si can never be the subject, nor sit inside one.
• In a subordinate clause, si looks to that clause's own subject.
• For each other, write unu la alian.
• For the door opened, write -iĝ-, not sin.