The correct spelling is “à tout à l’heure,” without an e in “tout”. The confusion with “à toute à l’heure” is based on a reflex of agreement with “heure,” a feminine word. This reflex is grammatically unfounded because “tout” does not relate to “heure” in this expression.
Grammatical function of “tout” in the expression “à tout à l’heure”
In “à tout à l’heure,” “tout” functions as an invariable adverb. It modifies the adverbial phrase “à l’heure” and carries the meaning of “entirely, completely.” We are not dealing with a determiner that would accompany the noun “heure.”
This is a point that normative grammars emphasize: “tout” as an adverb remains invariable before another adverb or an adverbial phrase. Writing “toute” would imply that “tout” agrees with a feminine noun it determines, which is not the case here.
To know how to write à tout à l’heure correctly, it is enough to identify this adverbial nature. If “tout” can be replaced by “complètement” without altering the meaning, it remains invariable.
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The only exception where “tout” as an adverb takes an e
The agreement of “tout” as an adverb exists, but in a specific context: before a feminine adjective starting with a consonant or a mute h. We write “elles sont toutes petites” (feminine adjective, initial consonant) but “elles sont tout étonnées” (feminine adjective, initial vowel).
This exception does not apply to “à tout à l’heure” because “tout” does not precede a feminine adjective. It precedes the preposition “à.” The rule of agreement with a feminine adjective starting with a consonant is strictly limited to this case.
Semiotic nuance between “à tout à l’heure” and “tout à l’heure”
Competing articles almost exclusively address spelling, but the difference in meaning between the two forms deserves attention. “À tout à l’heure” always points to the future: it is a farewell formula meaning “see you soon, on the same day.”
“Tout à l’heure” without the first “à” is more ambiguous. This adverbial phrase refers either to the recent past or the near future depending on the context:
- Past: “Tout à l’heure, je l’ai croisé dans le couloir” – the event occurred recently.
- Future: “On se voit tout à l’heure” – the event will take place a little later in the day.
- The initial preposition “à” in “à tout à l’heure” locks the meaning toward the future and transforms the phrase into a greeting formula.
This distinction is useful in writing, especially in professional exchanges where temporal precision matters. Saying “tout à l’heure” at the beginning of a sentence can create an ambiguity that the context does not always clarify.
Distinguishing “à tout à l’heure” and “à tout de suite” in French
Another source of confusion concerns the boundary between these two expressions. Both serve to say goodbye, but “à tout de suite” implies a near-immediacy, ranging from a few seconds to a few minutes. “À tout à l’heure” allows for a wider interval, which can extend to several hours, as long as it remains on the same day.
In formal situations, choosing one or the other is not trivial. If you leave a meeting to return after the coffee break, “à tout à l’heure” is appropriate. If you accompany someone to the door and return immediately, “à tout de suite” is more accurate.
Summary table of temporal farewell expressions
| Expression | Spelling | Temporal meaning |
|---|---|---|
| À tout à l’heure | “tout” invariable | Near future, same day |
| Tout à l’heure | “tout” invariable | Recent past or near future |
| À tout de suite | “tout” invariable | Near-immediacy |
| À la bonne heure | Fixed expression | Approval, no temporal value |
Method to stop writing “à toute à l’heure”
We recommend a two-step substitution test, quick to apply in any writing context.
First step: replace “tout” with “complètement.” If the sentence remains understandable (“à complètement à l’heure”), it is an adverb. An adverb does not take the feminine form, except for the exception mentioned above.
Second step: check if “tout” determines a noun. In “toute la journée,” “tout” is a determiner of “journée” (feminine singular), so it agrees. In “à tout à l’heure,” “tout” does not determine any noun, so there is no reason to write “toute.”
This double test also works for other fixed expressions where “tout” remains invariable: “tout de même,” “tout de suite,” “tout à fait.” In each case, “tout” is an adverb and does not agree.
- “Tout de même”: “tout” = “complètement” – invariable.
- “Tout à fait”: “tout” modifies “à fait” – invariable.
- “À tout à l’heure”: same logic, same result.
The mistake “à toute à l’heure” is classified among frequent errors in French spelling, alongside “quoique” confused with “quoi que.” In both cases, it is the grammatical nature of the word (adverb or determiner, conjunction or pronoun) that dictates the spelling. Identifying this nature resolves the doubt without resorting to pure memorization.
The rule can be summed up in one sentence: in any fixed adverbial expression, “tout” remains invariable. Systematically applying the substitution test with “complètement” is enough to eliminate the mistake, regardless of the writing situation.