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Imperfect Subjunctive vs Conditional: When They're Interchangeable

📋Overview🤝When They're Interchangeable: Polite Requests⚠️When You MUST Use Conditional🔒When You MUST Use Imperfect Subjunctive📖Quick Reference Guide

Overview

You've learnt that quisiera (imperfect subjunctive) and querría (conditional) both mean "I would like." But when can you use either one, and when must you choose a specific form?

This confusion exists because in some contexts, these forms are completely interchangeable, whilst in others, only one is grammatically correct. Understanding the difference will help you sound more natural and avoid mistakes.

🔗 Grammar Foundation

This article assumes you know how to form both tenses. If you need a refresher:

💡 The Quick Answer

Interchangeable: Polite requests with querer, poder, and similar verbs

Only Conditional: Hypothetical consequences, probability in the past

Only Imperfect Subjunctive: After "si" clauses, after subjunctive triggers, "como si"

When They're Interchangeable: Polite Requests

With verbs like querer (to want), poder (to be able), and deber (should), both forms work for polite requests. The imperfect subjunctive is often considered slightly more formal or polite, but both are perfectly acceptable.

Scenario 1: Restaurant - "I Would Like"

Both Forms Work:

Imperfect Subjunctive
Quisiera una mesa para dos.
I would like a table for two.
Slightly more formal/polite
Conditional
Querría una mesa para dos.
I would like a table for two.
Also polite, slightly less formal
Why both work:

Both forms soften the direct request "quiero" (I want). The choice is purely stylistic—some regions prefer one over the other, but neither is wrong.

Scenario 2: Asking for Help - "Could You"

Both Forms Work:

Imperfect Subjunctive
¿Pudieras ayudarme con esto?
Could you help me with this?
Very polite, somewhat formal
Conditional
¿Podrías ayudarme con esto?
Could you help me with this?
Polite, more commonly used
Regional note:

In Spain, you'll hear both equally. In Latin America, podrías (conditional) is more common in everyday speech, whilst pudieras sounds more formal or literary.

Scenario 3: Suggestions - "Should"

Both Forms Work:

Imperfect Subjunctive
Debieras descansar más.
You should rest more.
Gentle suggestion, slightly formal
Conditional
Deberías descansar más.
You should rest more.
Gentle suggestion, more common

When You MUST Use Conditional

In certain contexts, only the conditional is grammatically correct. Using the imperfect subjunctive here would be wrong.

Rule 1: Hypothetical Consequences (Main Clause)

When expressing what would happen in a hypothetical situation, you must use the conditional in the main clause:

✓ Correct:
Si tuviera dinero, compraría una casa.
If I had money, I would buy a house.
Conditional required for the consequence
✗ Wrong:
Si tuviera dinero, comprara una casa.
Cannot use imperfect subjunctive here
Why? The imperfect subjunctive goes in the "si" clause (the condition), whilst the conditional goes in the main clause (the result). This is a fixed structure.

Rule 2: Probability in the Past

When speculating about what probably happened in the past, use the conditional:

✓ Correct:
Serían las tres cuando llegó.
It was probably about three o'clock when he arrived.
Conditional for past speculation
✗ Wrong:
Fueran las tres cuando llegó.
Imperfect subjunctive doesn't express probability

Rule 3: Future in the Past (Reported Speech)

When reporting what someone said they would do, use the conditional:

✓ Correct:
Dijo que vendría mañana.
He said he would come tomorrow.
Conditional for reported future action
✗ Wrong:
Dijo que viniera mañana.
Wrong tense for reported speech

When You MUST Use Imperfect Subjunctive

In these situations, only the imperfect subjunctive is grammatically correct. Using the conditional would be a mistake.

Rule 1: After "Si" (If) Clauses

In the "if" part of a hypothetical sentence, you must use imperfect subjunctive:

✓ Correct:
Si tuviera tiempo, iría al cine.
If I had time, I would go to the cinema.
Imperfect subjunctive required after "si"
✗ Wrong:
Si tendría tiempo, iría al cine.
Never use conditional after "si"
⚠️ Common Mistake:

English says "If I would have..." but Spanish NEVER uses conditional after "si" in hypothetical sentences. Always use imperfect subjunctive.

Rule 2: After Subjunctive Triggers

Verbs and expressions that trigger the subjunctive require imperfect subjunctive in past contexts:

After verbs of wanting/requesting:
✓ Correct:
Quería que vinieras.
I wanted you to come.
✗ Wrong:
Quería que vendrías.
After expressions of doubt/emotion:
✓ Correct:
Dudaba que fuera verdad.
I doubted it was true.
✗ Wrong:
Dudaba que sería verdad.

Rule 3: After "Como Si" (As If)

"Como si" (as if) always requires imperfect subjunctive, never conditional:

✓ Correct:
Habla como si fuera experto.
He speaks as if he were an expert.
Always imperfect subjunctive after "como si"
✗ Wrong:
Habla como si sería experto.
"Como si" never takes conditional

Quick Reference Guide

Decision Framework

✓ BOTH work (interchangeable)
  • Polite requests with querer, poder, deber
  • Example: Quisiera / Querría un café
  • Choice is stylistic—imperfect subjunctive slightly more formal
→ ONLY Conditional
  • Main clause in hypothetical sentences
  • Example: Si tuviera dinero, compraría una casa
  • Probability in the past
  • Example: Serían las tres (It was probably 3 o'clock)
  • Future in the past (reported speech)
  • Example: Dijo que vendría (He said he would come)
→ ONLY Imperfect Subjunctive
  • After "si" in hypothetical sentences
  • Example: Si tuviera dinero, compraría una casa
  • After subjunctive triggers (querer que, dudar que, etc.)
  • Example: Quería que vinieras
  • After "como si" (as if)
  • Example: Como si fuera fácil

⚡ The Most Common Mistake

Never use conditional after "si":

✗ Si tendría dinero...
✓ Si tuviera dinero...

🔗 Continue Learning

Now that you understand when to use each form, deepen your knowledge: