As if + imperfect subjunctive (English equivalent: 'as if' + past-tense/subjunctive clause to express unreality — e.g., 'as if he were...')

Como si + imperfect subjunctive — meaning and use

The Spanish construction como si + imperfect subjunctive is a common way to make a comparison that is hypothetical, contrary to fact, or simply imagined. In English it usually translates as "as if" or "as though" plus a past-tense form that shows the idea is not real (for example: as if he were, as if she had, as if they knew).

Example (present unreal):
- Se comporta como si fuera el jefe. (He behaves as if he were the boss — but he is not.)

Use this structure when you want to describe how something appears, how someone acts, or to suggest an unreal or imagined situation.

When do I use it?

- To describe an unreal or contrary-to-fact situation in the present: use the imperfect subjunctive after como si.
- Ella habla como si supiera todo. (She speaks as if she knew everything — but she doesn't.)

- To describe how someone behaved in the past when the imagined situation is simultaneous with that past moment: use the imperfect subjunctive.
- Me miró como si no me conociera. (He looked at me as if he didn't know me.)

- To describe an imagined event that happened before a past moment (anterior): use the pluperfect subjunctive (hubiera/hubiese + past participle) after como si.
- Me miró como si no me hubiera conocido nunca. (He looked at me as if he had never known me.)

- For commands or prohibitions: use imperfect subjunctive after como si.
- No me trates como si fuera un niño. (Don't treat me as if I were a child.)

How does this compare to English?

English uses "as if" or "as though" with a past tense to indicate unreality: "He acts as if he knew everything." Spanish uses como si + imperfect subjunctive: "Él actúa como si supiera todo."

How do I form the imperfect subjunctive?

Step-by-step formation
1) Start with the third-person plural of the preterite (ellos form). Example: hablar -> hablaron; comer -> comieron; vivir -> vivieron.
2) Drop the -ron ending to get the stem: hablaron -> habla- ; comieron -> comie- ; vivieron -> vivie- .
3) Add one of two sets of endings: the -ra set (more common in spoken/written Spanish) or the -se set (also correct, slightly more formal or literary).

- -ra endings: -ra, -ras, -ra, -ramos, -rais, -ran
- -se endings: -se, -ses, -se, -semos, -seis, -sen

Examples (both forms):
- hablar: hablara / hablase (yo hablara, yo hablase)
- comer: comiera / comiese
- vivir: viviera / viviese
- ser / ir: fuera / fuese
- tener: tuviera / tuviese
- estar: estuviera / estuviese
- poder: pudiera / pudiese

Note: the nosotros form often carries an accent to keep the normal stress: habláramos / hablásemos; fuéramos / fuésemos.

Pluperfect subjunctive (for past anterior comparisons)
To talk about an imagined action that happened before the time of the main verb, use hubiera or hubiese + past participle (pluscuamperfecto de subjuntivo):
- como si hubiera visto, como si hubiese entendido

Example: Lo contó como si lo hubiera vivido. (He told it as if he had lived it.)

How do I choose imperfect vs pluperfect after como si?

- Use imperfect subjunctive (supiera, fuera, tuviera, etc.) when the imagined situation is simultaneous with the time of the main clause (present or past).
- Present main clause: Habla como si supiera la respuesta. (He speaks as if he knew the answer — now.)
- Past main clause (simultaneous): Habló como si supiera la respuesta. (He spoke as if he knew the answer at that time.)

- Use pluperfect subjunctive (hubiera/hubiese + participle) when the imagined situation happened before the time of the main clause.
- Past main clause (anterior action): Habló como si hubiera sabido la respuesta antes de la reunión. (He spoke as if he had known the answer before the meeting.)

Note: in everyday speech some speakers may use the imperfect subjunctive where strict grammar would prefer the pluperfect, but the pluperfect makes the anterior time relation clear.

Comprehensive examples with translations

Present or general unreal comparisons
- Habla como si supiera todo. (He speaks as if he knew everything.)
- Se comporta como si fuera el jefe. (She behaves as if she were the boss.)
- Corre como si pudiera volar. (He runs as if he could fly.)
- Ríe como si no existiera ningún problema. (She laughs as if there were no problems.)

Commands and prohibitions
- No me trates como si fuera un niño. (Don't treat me as if I were a child.)
- No vengas a mí como si supieras la solución. (Don't come to me as if you knew the solution.)

Different subjects in main and subordinate clause
- Actúas como si yo fuera el problema. (You act as if I were the problem.)
- Habla de su trabajo como si viviera en otro país. (He talks about his work as if he lived in another country.)

Progressive / ongoing action with imperfect subjunctive + gerund
- Sale de la casa como si estuviera buscando algo. (She leaves the house as if she were looking for something.)
- Habla como si estuviera dictando órdenes. (He speaks as if he were giving orders.)

Two variants (-ra and -se) shown side by side
- Parece como si estuviera soñando. / Parece como si estuviese soñando. (It seems as if she were dreaming.)
- Ella actúa como si fuera/ fuese la dueña. (She acts as if she were the owner.)

Common mistakes and how to avoid them

- Using the indicative instead of the subjunctive when the comparison is unreal.
- Wrong: El actúa como si sabe todo.
- Correct: Él actúa como si supiera todo.

- Using the conditional in the subordinate clause (this is incorrect after como si).
- Wrong: No me hables como si me ayudarías.
- Correct: No me hables como si me ayudaras.

- Adding que after como si (unnecessary and incorrect).
- Wrong: Se comporta como si que fuera importante.
- Correct: Se comporta como si fuera importante.

- Confusing when to use imperfect vs pluperfect subjunctive. Decide whether the imagined action is simultaneous with the main verb (use imperfect subjunctive) or happened earlier (use pluperfect subjunctive: hubiera/hubiese + participle).

How this differs from similar structures

Como vs como si
- Como + noun/adjective = 'as' or 'in the capacity of'. Example: Como profesora, ella sabe enseñar. (As a teacher, she knows how to teach.)
- Como si + subjunctive = 'as if' or 'as though' (comparison, often unreal). Example: Ella se comporta como si fuera profesora. (She behaves as if she were a teacher.)

Quick checklist for learners

- Use como si + imperfect subjunctive to talk about unreal or imagined comparisons in the present or simultaneous past.
- Use como si + hubiera/hubiese + past participle (pluperfect subjunctive) when the imagined action is anterior to the main clause.
- Do not add que after como si.
- Do not use the conditional or the indicative when you mean an unreal comparison; use the subjunctive.
- Both -ra and -se forms of the imperfect subjunctive are correct; -ra is more common in everyday speech.

Glossary

- Subjunctive: a mood that expresses doubt, desire, uncertainty, or unreality.
- Imperfect subjunctive (imperfecto de subjuntivo): past form of the subjunctive used to talk about hypothetical or contrary-to-fact situations (examples: fuera, supiera, tuviera).
- Pluperfect subjunctive (pluscuamperfecto de subjuntivo): formed with hubiera/hubiese + past participle; used for imagined actions that are prior to another past action (example: hubiera visto).
- Indicative: the mood used to state facts and real events (not used after como si when you mean an unreal comparison).
- Simultaneous: happening at the same time as the main action (use imperfect subjunctive after como si).
- Anterior: happening before the main action (use pluperfect subjunctive after como si).

Summary: When you want to say that something appears or is being compared to an imagined situation, think "as if" — and in Spanish use como si + the subjunctive. For present or simultaneous unreality use the imperfect subjunctive (supiera, fuera); for an imagined action that preceded the main action use the pluperfect subjunctive (hubiera/hubiese + participle).