The hesitation between “tous les deux” and “tout les deux” is one of the recurring pitfalls of written French. The correct form in the masculine is “tous les deux,” with a final -s. In the feminine, we write “toutes les deux.” The spelling “tout les deux” without -s is a mistake, regardless of the context.
This rule is based on the functioning of the word “tout” as an indefinite determiner, which agrees in gender and number with the noun or pronoun it accompanies. Understanding this mechanism allows one to avoid hesitation, even in more complex constructions.
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Agreement of “tout” before a plural determiner: the grammatical mechanism
The word “tout” changes form according to its function in the sentence. When it precedes a definite article (le, la, les) followed by a noun or pronoun, it acts as an indefinite determiner. As such, it agrees in gender and number with the element it determines.
Before “les deux,” the group designates a plural set. The determiner “tout” therefore takes the plural mark: “tous” in the masculine, “toutes” in the feminine. The form “tout les deux” is incorrect because it associates a singular (tout) with a plural (les deux).
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A detailed guide explains the logic behind the agreement of tous les deux or toutes les deux on Recommandons, with concrete examples to memorize the rule.
What blurs the lines is that “tout” also exists as an invariable (or almost) adverb in other constructions. In “elles sont tout étonnées,” “tout” is an adverb and does not agree in the same way. The confusion between these uses explains a good part of the errors.
Masculine, feminine, mixed: how to agree “tous les deux” according to gender
The agreement rule follows the classic pattern of French.
- Two masculine referents or a mixed group (masculine + feminine): we write “tous les deux”, with “tous” in the masculine plural. Example: “Marc and Julie are both leaving this morning.”
- Two feminine referents: we write “toutes les deux”, with “toutes” in the feminine plural. Example: “My two sisters both arrived yesterday.”
- When the gender of the referents is not explicit in the sentence, the masculine prevails by default according to traditional grammar. This convention is sometimes contested in discussions about inclusive writing, but it remains the norm in reference grammars.
The most frequent trap concerns mixed groups. As soon as a single masculine element is present, the agreement is made in the masculine plural. “Paul and Marie are both concerned” is the only correct spelling.
“Tous deux” or “tous les deux”: common and formal registers
Both forms are grammatically correct, but they do not belong to the same register. “Tous les deux” is the standard form, used both orally and in writing in everyday language. “Tous deux” (without the article “les”) is perceived as more literary, more formal.
Documented discussions on specialized forums confirm this distinction. “Tous deux” is encountered more in narrative texts, formal correspondence, or essays. In a professional email or conversation, “tous les deux” remains the natural choice.
The same logic applies to the feminine: “toutes deux” is more formal than “toutes les deux.” The meaning does not change; only the level of language varies. The choice depends on the writing context, not a correction rule.
Extension to other numbers: tous les trois, toutes les quatre
The competing articles are almost always limited to “deux,” but the agreement logic works the same for other small numbers. We write “tous les trois,” “toutes les trois,” “tous les quatre,” “toutes les quatre,” respecting the same agreement principle in gender.
The value of these expressions is that of a set. “They are all three graduates” means that each of the three, without exception, holds a diploma. The omission of the article remains possible in a formal register: “tous trois,” “toutes quatre.”
This extension is useful to know because it shows that the rule is not an isolated case related to the number two. It is a regular grammatical mechanism, applicable whenever we refer to a counted group preceded by “tout.”
Differentiating “tout” adverb and “tout” determiner: the source of errors
The majority of mistakes regarding “tous les deux” stem from a confusion between two uses of the word “tout.”
As a determiner, “tout” always agrees with the noun or pronoun: tous (masculine plural), toutes (feminine plural), tout (masculine singular), toute (feminine singular). This is the case in “tous les deux,” “toute la journée,” “tous les matins.”
As an adverb, “tout” means “entirely” or “completely.” It is generally invariable: “they are all happy.” The exception concerns feminine adjectives starting with a consonant or a silent h, where the adverb takes the feminine mark for phonetic reasons: “they are all happy” (the -s and -e allow for liaison).
- “Tout” determiner before “les deux”: mandatory agreement in gender and number. “Tous les deux,” “toutes les deux.”
- “Tout” adverb before an adjective: invariable except in the feminine before a consonant or silent h. “All happy,” “all surprised.”
- “Tout” pronoun (“all came”) : variable in gender and number, and the -s of “tous” is pronounced in this case.
This distinction between adverb and determiner is the real crux of the difficulty. Once we identify the function of “tout” in the sentence, the agreement becomes mechanical.
The next time hesitation arises, the question to ask is simple: does “tout” accompany a plural group introduced by an article? If so, it takes the plural mark. In the masculine, “tous les deux” with an -s is the only correct form. In the feminine, “toutes les deux” with -es. No exceptions, no special cases.