With an infinitive, si, sin, and sia point to the person or thing understood to perform that infinitive’s action. That understood participant is the infinitive’s semantic subject. It is often the main-clause subject, but verbs of asking, ordering, allowing, or causing can assign the infinitive to someone else.
Start with the ordinary reflexive system
Si is third person and reflexive. It never serves as a subject. Sin is its accusative form, and sia is the possessive adjective; sia agrees with the possessed thing, not with its owner.
| Role inside the infinitive | Form | Example |
|---|---|---|
| after a preposition | si | zorgi pri si |
| direct object | sin | lavi sin |
| possessor | sia | preni sian sakon |
Ĉiu devas zorgi pri si mem.
Everyone must take care of themself.
— Kion Marta volas fari antaŭ la vespermanĝo? — Ŝi volas lavi sin.
— What does Marta want to do before dinner? — She wants to wash herself.
La vojaĝantoj esperas retrovi siajn valizojn.
The travelers hope to recover their own suitcases.
In all three examples, the main subject also performs the infinitive: everyone does the caring, Marta does the washing, and the travelers do the recovering. The reflexive therefore points to that shared participant.
Subject control: the main subject performs both actions
After verbs such as voli, povi, devi, provi, esperi, promesi, and decidi, the main-clause subject normally controls the infinitive. A third-person controller licenses si/sin/sia.
Li promesis ne plu mensogi al si mem.
He promised not to lie to himself anymore.
Ŝi decidis vendi sian aŭton kaj veturi per trajno.
She decided to sell her car and travel by train.
Ĉu la infanoj povas mem prepari sian matenmanĝon?
Can the children prepare their own breakfast themselves?
The reflexive is still third person. When the controller is mi, ni, or vi, repeat that ordinary pronoun family instead:
Mi volas prezenti min al la nova teamo.
I want to introduce myself to the new team.
Vi devas kunporti vian pasporton.
You must bring your passport.
English uses “myself/yourself” and “one’s own,” but Esperanto’s dividing line is grammatical person: si replaces only a third-person form.
Object control: another participant performs the infinitive
With peti, ordoni, permesi, malpermesi, konsili, and similar verbs, a complement can identify who performs the infinitive. Then the reflexive points to that complement, not automatically to the main subject.
La estro petis la novan kolegon prezenti sin.
The manager asked the new colleague to introduce themself.
La kuracisto konsilis al Marta doni al si pli da tempo por ripozi.
The doctor advised Marta to give herself more time to rest.
La patro ne permesis al la infanoj iri solaj al la rivero.
The father did not allow the children to go to the river alone.
In the first, the colleague presents the colleague; in the second, Marta gives time to Marta. The main subjects la estro and la kuracisto do not control those infinitives.
Compare the meaning contrast:
La sinjoro ordonis al la servisto vesti sin.
The gentleman ordered the servant to dress himself—the servant.
La sinjoro ordonis al la servisto vesti lin.
The gentleman ordered the servant to dress him—most naturally, the gentleman.
Sin is not a vague “same person somewhere earlier” marker. It selects the semantic subject of vesti, namely la servisto. Lin deliberately points to another male person.
Generic infinitives
An infinitive can have a general human subject rather than a named controller. Reflexive si then means whoever performs the activity.
Estas malfacile pardoni al si post grava eraro.
It is difficult to forgive oneself after a serious mistake.
Ne estas permesite foti sin en tiu parto de la muzeo.
It is not permitted to photograph oneself in that part of the museum.
Por bone koni sin, necesas aŭskulti ankaŭ kritikojn.
To know oneself well, one must also listen to criticism.
The entire infinitive phrase can itself be the subject of an impersonal evaluation. That does not violate the rule that si cannot be a subject: si is an object or complement inside the infinitive, whose semantic subject is generic.
When the infinitive’s agent is omitted
The hardest cases contain an infinitive whose actual performer is not named. With constructions such as sendi voki or lasi fari, usage often treats the verb sequence as one unit. When the omitted performer is unimportant, si/sia can point back to the main subject.
La reĝino sendis voki sian kuraciston.
The queen sent for her own doctor.
No named person performs voki, so sian naturally refers to la reĝino. Once an infinitive performer is made explicit, the reference changes:
La reĝino sendis la serviston voki ŝian kuraciston.
The queen sent the servant to call her—the queen’s—doctor.
La reĝino sendis la serviston voki sian kuraciston.
The queen sent the servant to call his own doctor.
In the last sentence, la servisto is the semantic subject of voki, so sian belongs to the servant. This is a real structural contrast. Repeating la kuraciston de la reĝino is preferable when several same-gender referents make ŝian ambiguous.
Similar variation occurs with lasi + infinitive. If no agent of the infinitive appears, standard usage often lets the main subject control a reflexive:
Ŝi lasis sin foti antaŭ la teatro.
She let herself be photographed in front of the theater.
If the photographer is introduced, use the ordinary object pronoun: Ŝi lasis la ĵurnaliston foti ŝin. The journalist takes the photograph; ŝin is the photographed person.
Norm, variation, and clarity
The Akademio’s official decision on reflexives recognizes that an infinitive can introduce the relevant logical subject for si. PMEG describes the same principle in terms of the infinitive’s semantic subject. The stable core is therefore normative, not a recent stylistic fashion.
Variation begins when the infinitive’s performer is omitted. Historical texts sometimes use an ordinary pronoun where modern analysis recommends si/sia. For neutral international prose, name the controller or recast the sentence whenever two analyses are plausible. Deeply nested infinitives are difficult even for experienced readers.
For a broader account of control, see Subject Control with Infinitives.
Common Mistakes
Letting si point to the main subject despite an explicit controller
❌ La patrino petis sian filon porti sian valizon.
Wrong for the intended meaning ‘the mother’s suitcase’ — the son performs porti, so sian means the son’s.
✅ La patrino petis sian filon porti ŝian valizon.
The mother asked her son to carry her suitcase.
Using si for first person
❌ Mi volas defendi sin kontraŭ tiu akuzo.
Incorrect — si is only third person.
✅ Mi volas defendi min kontraŭ tiu akuzo.
I want to defend myself against that accusation.
Using si as the infinitive’s subject
❌ Karlo volas si resti hejme.
Incorrect — si cannot serve as a subject.
✅ Karlo volas resti hejme.
Karlo wants to stay home.
Making sia agree with the possessor
❌ La studentoj volas vendi sia libro.
Incorrect — singular libro requires singular sia.
✅ La studentoj volas vendi sian libron.
The students want to sell their own book.
Key Takeaways
- With an infinitive, si/sin/sia refers to the infinitive’s semantic subject.
- The main subject often controls the infinitive, but an explicit object or al complement can control it instead.
- Use mi/min/mia, ni/nin/nia, and vi/vin/via for first- and second-person reflexive meaning.
- If an infinitive’s agent is omitted, some verb sequences act as one unit; make the agent explicit when reference could be disputed.
- Sia agrees with the possessed noun, never with the controller.
Related Topics
- The Reflexive Pronoun SiA1 — Use si and sin when a third-person subject refers back to itself, and distinguish reflexive reference from ordinary third-person pronouns.
- Clause Boundaries for SiA1 — Track si and sia within finite clauses so that reflexive reference stays with the correct local subject.
- Infinitive SubjectsA1 — Use an infinitive phrase as a clause subject, describe its action with an adverb, and identify its understood actor clearly.
- Subject Control with InfinitivesA2 — Identify the understood actor of an infinitive after same-subject, influence, perception, causative, and purpose constructions.
- Infinitives as ComplementsA1 — Build verb chains with an -i infinitive, assign its understood subject, and keep tense, negation, objects, and clause boundaries clear.