Si au présent: never with the future or conditional

If French grammar has a single iron law that every learner must internalize, it is this: si is never followed by the futur, and si is never followed by the conditionnel. Si — the conjunction "if" — introduces a clause whose tense is fixed by the type of conditional you are building, and the choice is always between three indicative forms: présent (for real or open conditions), imparfait (for hypothetical or counterfactual present), or plus-que-parfait (for counterfactual past). The futur and the conditional belong in the main clause, never inside the si-clause itself. The French schoolchildren's mnemonic is les "si" n'aiment pas les "rais" — "si doesn't like -rais" — meaning si-clauses don't take verb forms ending in -rais (imperfect or conditional endings beginning with -r). This page covers the three conditional types, the rationale for the si + présent rule, the contrast with quand, and the common errors that this single rule prevents.

The three conditional types

Every French conditional sentence falls into one of three structural types, distinguished by the speaker's stance toward the condition.

Notice that the si-clause never takes the futur and never takes the conditionnel — across all three types. The futur and conditional are confined to the main clause.

Type 1: si + présent + futur (real conditions)

Type 1 is the most common conditional in everyday French. It expresses a condition that is genuinely possible — neither presupposed (like quand) nor counterfactual (like Types 2 and 3). The si-clause is in the présent, and the main clause is typically in the futur (or sometimes the imperative or présent).

In the first three, the main clause is in the futur; in the last two, it's an imperative. All five si-clauses are in the présent. The English equivalent — if you come, if I pass, if it rains tomorrow — is also in the present, so the structure parallels English here. This is fortunate; it makes Type 1 the easiest type to master.

Note the elision: si + il = s'il, si + ils = s'ils. Si does not elide before any other vowel (si elle, si on, si Anne, si Étienne — all unelided).

Type 2: si + imparfait + conditionnel présent (hypothetical)

Type 2 expresses a hypothetical or unreal present situation, or a counterfactual future. The speaker is typically saying: "I'm imagining a world in which X — but X isn't actually the case (or is unlikely)."

The si-clause is in the imparfait (avais, étais, aimais, partait) and the main clause in the conditionnel présent (viendrais, achèterais, dirais, arriverait). The English equivalent is if I had ... I would, with the past-tense form in the if-clause and the modal would in the main clause.

A common Type 2 use is the polite request or suggestion:

These standalone si-clauses (no main clause) propose a hypothetical action softly. They are entirely conversational and use the imparfait alone.

Type 3: si + plus-que-parfait + conditionnel passé (counterfactual past)

Type 3 looks back at a past situation and imagines how it could have unfolded differently. The condition did not occur; the speaker is imagining its alternative.

The si-clause is in the plus-que-parfait (avais eu, avais appelé, était partis, avait su) and the main clause in the conditionnel passé (serais venu, aurais aidé, aurait raté, serait venue). Auxiliary choice and participle agreement follow standard rules.

Type 3 sentences are everywhere in regret, blame, and counterfactual reasoning. They are the past-tense version of "would have." Notice that the conditional passé contains a futur form of the auxiliary in the conditional — but the si-clause itself is in the plus-que-parfait, an indicative tense, not a conditional one. The si-rule holds.

Mixed types: when types blend

Real conversation sometimes mixes a past condition with a present consequence (mixed Type 3 + Type 2):

The si-clause stays in the plus-que-parfait, and the main clause uses the conditionnel présent rather than the conditionnel passé. This communicates a present consequence of a past unrealized condition.

The same pattern can run the other way: a present condition with a past consequence is rare but possible:

The point is that even in mixed conditionals, the si-clause never takes the futur or the conditionnel. The mixing happens at the boundary between the si-clause's indicative tense and the main clause's conditional form.

Why si never takes the futur or conditional

The structural reason is that French treats si as a "neutral hypothetical" subordinator. The si-clause is not a temporal location of an event — it is the suspension of an event from the timeline, a mental exploration of what would happen if something were true. Indicative tenses (présent, imparfait, plus-que-parfait) provide the right semantic neutrality for this purpose. The futur, by contrast, anchors an event firmly to the future timeline; using it in a si-clause would assert that the event will happen, contradicting the very purpose of si.

The conditionnel, in turn, is reserved for the consequence of a hypothetical condition, never the condition itself. Putting the conditionnel in a si-clause would create a self-referential loop ("if it would happen, then it would happen") that French grammar rejects.

This is not just a French quirk. Spanish behaves similarly: si vienes, vendré ("if you come, I'll come") uses the present in the si-clause and the future in the main clause, with the same constraint on no future or conditional after si. Italian se works the same way. The pattern is consistent across the Romance languages.

The asymmetry with quand

This is where the si rule and the quand rule come into sharpest contrast. Both can introduce clauses about future events, but they encode opposite stances and require opposite tenses.

The two sentences differ only in the conjunction (quand vs si) and the tense of the subordinate verb (viendras vs viens). Their meanings differ at exactly that point: quand presupposes the event, si leaves it open. This is one of the cleanest examples in French of how a tense choice encodes a meaning choice.

When deciding between si and quand in a future-oriented clause, ask: is the event presupposed or open?

• Presupposed ("it will happen, the question is when") → quand
  • futur
• Open ("it might happen, in which case...") → si
  • présent

Si in indirect questions

There is one si that does take other tenses freely, and it is not the conditional si discussed here: it is the si of indirect questions, equivalent to English "whether" or "if" in reported questions.

In these sentences, si introduces a yes/no question embedded inside a verb of inquiry (demander, savoir, dire). It is not the conditional si. This si takes whatever tense the embedded question requires — including the futur and the conditional. This is the only si that can be followed by the futur or the conditionnel in modern French.

How to tell which si you have: if the si-clause can be replaced with English whether, it's the indirect-question si and the conditional rules don't apply. If the si-clause expresses a condition for the main clause, it's the conditional si and the les "si" n'aiment pas les "rais" rule applies.

Common Mistakes

The most common transfer error from English speakers who have learned the quand + futur rule and try to extend it to si. The two rules are opposite: quand takes futur for projected events; si takes présent for real conditions.

The classic les "si" n'aiment pas les "rais" error. The conditional belongs in the main clause; the si-clause requires the imparfait for hypothetical conditions.

This particular error — si j'aurais su instead of si j'avais su — is so notorious in French that it became the title of the comedy Les Visiteurs mock-up Si j'aurais su, j'aurais pas venu, used to mark uneducated speech. Native French speakers who say si j'aurais are corrected immediately. The correct form is always si j'avais (plus-que-parfait).

Same error, present-tense version: si tu serais instead of si tu étais. The conditional cannot appear after si.

A purely orthographic error: si must contract to s' before il and ils. It does not contract before any other vowel (si elle, si on, si Antoine are all correct unelided).

Key takeaways

The rule is short and unconditional: si never takes the futur and never takes the conditionnel. The si-clause is always in the présent (Type 1, real conditions), the imparfait (Type 2, hypothetical), or the plus-que-parfait (Type 3, counterfactual past). The futur and the conditional live in the main clause. The contrast with quand — which takes the futur for projected future events — is the most important asymmetry in French temporal and conditional syntax. Master both rules together: quand + futur for "when something will happen," si + présent for "if something happens." Once these two patterns are reflexive, your French sentences about the future will be correct in the great majority of cases, and you will have crossed one of the most decisive accuracy thresholds at B1.