Mentir is the verb to lie — to deliberately say something untrue. It belongs to the partir family of irregular -ir verbs (3e groupe): same conjugation pattern as partir, sortir, dormir, sentir, servir. The hallmark of the family is the consonant alternation between singular and plural in the present (je mens / nous mentons) and in compound tenses with avoir, never être.
The English speaker's first big trap is the homonym "to lie": in English, the same word covers two unrelated actions — telling falsehoods and reclining horizontally. French keeps these strictly separate. Mentir is only deception; lying down is s'allonger or se coucher. Under no circumstance does mentir mean to lie on a sofa.
This page is the full reference: every paradigm, the constructions (mentir à quelqu'un, mentir sur quelque chose), the family compound démentir (to deny, refute), and the major idioms.
The conjugation pattern
The signature pattern of the partir-sortir-dormir group: in the singular, the consonant before the ending drops (ment- loses its t, leaving men-); in the plural, it returns (nous mentons). Spelling: drop the t in the singular only.
Présent de l'indicatif
| Person | Form | Pronunciation |
|---|---|---|
| je | mens | /mɑ̃/ |
| tu | mens | /mɑ̃/ |
| il / elle / on | ment | /mɑ̃/ |
| nous | mentons | /mɑ̃.tɔ̃/ |
| vous | mentez | /mɑ̃.te/ |
| ils / elles | mentent | /mɑ̃t/ |
The three singular forms are pronounced identically — mens, mens, ment are all /mɑ̃/. The t is silent. It only becomes audible in the plural (mentons, mentez, mentent), where it sits between vowels.
Tu mens, je le vois dans tes yeux.
You're lying, I can see it in your eyes.
Il ment comme il respire.
He lies as easily as he breathes.
Les chiffres ne mentent pas.
The numbers don't lie.
Imparfait
Built on the nous stem ment- + regular endings.
| Person | Form |
|---|---|
| je | mentais |
| tu | mentais |
| il / elle / on | mentait |
| nous | mentions |
| vous | mentiez |
| ils / elles | mentaient |
Note: nous mentions (imparfait) is identical to the noun les mentions (mentions, references). Context disambiguates.
Quand j'étais petit, je mentais à mes parents pour pouvoir sortir.
When I was little, I used to lie to my parents to be allowed out.
Elle mentait par habitude, sans même s'en rendre compte.
She lied out of habit, without even realizing it.
Passé simple (literary)
| Person | Form |
|---|---|
| je | mentis |
| tu | mentis |
| il / elle / on | mentit |
| nous | mentîmes |
| vous | mentîtes |
| ils / elles | mentirent |
Circumflex on mentîmes and mentîtes — required.
Il mentit pour protéger son ami.
He lied to protect his friend. (literary)
Futur simple
The futur stem is the full infinitive mentir-. Standard endings.
| Person | Form |
|---|---|
| je | mentirai |
| tu | mentiras |
| il / elle / on | mentira |
| nous | mentirons |
| vous | mentirez |
| ils / elles | mentiront |
Je ne te mentirai jamais, tu peux me croire.
I'll never lie to you, you can believe me.
On mentira si on doit le faire pour la sauver.
We'll lie if we have to do it to save her.
Conditionnel présent
Same stem mentir-, with imparfait endings.
| Person | Form |
|---|---|
| je | mentirais |
| tu | mentirais |
| il / elle / on | mentirait |
| nous | mentirions |
| vous | mentiriez |
| ils / elles | mentiraient |
Je mentirais si je disais que tout va bien.
I'd be lying if I said everything was fine.
Subjonctif présent
Stem ment- (from ils mentent without -ent).
| Person | Form |
|---|---|
| (que) je | mente |
| (que) tu | mentes |
| (qu')il / elle / on | mente |
| (que) nous | mentions |
| (que) vous | mentiez |
| (qu')ils / elles | mentent |
The subjonctif nous mentions and vous mentiez are spelled identically to the imparfait — context (a que trigger) selects the mood.
Je ne crois pas qu'il mente, il a l'air sincère.
I don't think he's lying, he seems sincere.
Il faut que tu mentes un peu pour ne pas la blesser.
You'll have to lie a little so as not to hurt her.
Impératif
| Person | Form |
|---|---|
| (tu) | mens |
| (nous) | mentons |
| (vous) | mentez |
Imperative mentez ! (lie!) is rare on its own — usually negated: ne mens pas !
Ne me mens pas, je sais où tu étais hier soir.
Don't lie to me, I know where you were last night.
Ne mentez plus, ça finit toujours par se savoir.
Stop lying, it always comes out in the end.
Participles and gérondif
- Participe passé: menti — invariable. Mentir is intransitive (object is introduced by à, not direct), so no possible direct-object agreement.
- Participe présent: mentant
- Gérondif: en mentant
Il a obtenu le poste en mentant sur son CV.
He got the job by lying on his résumé.
Une personne mentant systématiquement perd toute crédibilité.
Someone who systematically lies loses all credibility.
Compound tenses (with avoir)
Mentir takes avoir in all compound tenses. Despite the moral weight of the act, lying is not in the maison d'être — that list is reserved for verbs of motion and change of state. The participle menti is invariable.
Passé composé
avoir (présent) + menti
Tu m'as menti, et c'est ça qui me fait le plus mal.
You lied to me, and that's what hurts me most.
Il a menti à la police pour couvrir son frère.
He lied to the police to cover for his brother.
On a tous menti à un moment ou à un autre.
We've all lied at one point or another.
Plus-que-parfait
avoir (imparfait) + menti
J'ai compris trop tard qu'elle m'avait menti pendant des années.
I realized too late that she had been lying to me for years.
Futur antérieur
avoir (futur) + menti
Quand on découvrira la vérité, on saura qui aura menti.
When the truth comes out, we'll know who will have lied.
Conditionnel passé
avoir (conditionnel) + menti
Je n'aurais jamais menti pour si peu.
I would never have lied for something so trivial.
Major uses
1. Mentir à quelqu'un — to lie to someone
The construction is always with à for the recipient of the lie. Mentir is intransitive in French — you cannot mentir a person. You lie to them.
Pourquoi tu mens à ta mère ?
Why are you lying to your mother?
Il a menti à tout le monde, y compris à sa propre famille.
He lied to everyone, including his own family.
Je ne mens jamais à mes amis.
I never lie to my friends.
2. Mentir sur quelque chose — to lie about something
For the topic of the lie, the preposition is sur.
Elle a menti sur son âge pour avoir le poste.
She lied about her age to get the job.
Il ment sur tout : son passé, son travail, sa famille.
He lies about everything: his past, his job, his family.
3. Statements ascribing lies to non-human subjects
Sayings and proverbs personify objects or numbers as either truthful or lying.
Les chiffres ne mentent pas.
The numbers don't lie.
Son sourire ne ment pas, elle est vraiment heureuse.
Her smile doesn't lie, she's really happy.
L'image ne ment pas.
The picture doesn't lie.
4. Sans mentir — without exaggeration, honestly
A frequent fixed expression introducing a strong claim, asserting that the speaker isn't embellishing.
Sans mentir, je crois que c'est le meilleur film de l'année.
Honestly, I think it's the best film of the year.
Sans mentir, on a attendu deux heures dans le froid.
No exaggeration, we waited two hours in the cold.
High-frequency idioms
- mentir comme un arracheur de dents — to lie like a tooth-puller (i.e. shamelessly; the old metaphor: traveling tooth-pullers used to swear extraction was painless)
- mentir comme on respire — to lie as easily as one breathes (= to lie constantly, naturally)
- un mensonge gros comme une maison — a whopping lie (literally "a lie as big as a house")
- un pieux mensonge — a white lie, a lie told for kindness
- à beau mentir qui vient de loin — those returning from far away can spin tall tales (proverb: travelers are believed because no one can check)
- qui vole un œuf vole un bœuf — one lie / theft leads to bigger ones (related theme — small dishonesty escalates)
- les paroles s'envolent, les écrits restent — spoken words fly away, written words remain (the warning about lying in writing)
Il ment comme un arracheur de dents, ne crois pas un mot de ce qu'il dit.
He lies through his teeth, don't believe a word he says.
C'était un pieux mensonge pour ne pas la décevoir.
It was a white lie to spare her disappointment.
Elle nous a sorti un mensonge gros comme une maison.
She told us a whopping lie.
Démentir — to deny, refute, contradict
A high-frequency compound built on mentir. Démentir means to officially deny or refute — typically used for governments, companies, and public figures denying claims, or for evidence contradicting a theory.
| Person | Form (présent) |
|---|---|
| je | démens |
| tu | démens |
| il / elle | dément |
| nous | démentons |
| vous | démentez |
| ils / elles | démentent |
Past participle démenti. Same auxiliary (avoir).
Le ministre a démenti les rumeurs de démission.
The minister denied the resignation rumors.
Les faits démentent ses affirmations.
The facts contradict his claims.
L'entreprise dément formellement ces allégations.
The company formally denies these allegations.
A useful related noun: un démenti = an official denial (as a public-relations move). La présidence a publié un démenti = "The presidential office issued a denial."
Comparison with English
Three friction points:
English "to lie" is two verbs in disguise: tell-falsehood vs recline. French strictly separates them. Mentir = deceive only. S'allonger / se coucher = recline. Don't try to use mentir for "the dog is lying on the rug" — that is le chien est allongé sur le tapis.
English "lie to / lie about" maps to à / sur, not the same preposition. Mentir à quelqu'un (to a person), mentir sur quelque chose (about a topic). Don't say mentir sur ma mère if you mean lying to her — that would mean lying about her.
English "I haven't lied" maps to je n'ai pas menti with invariable participle. Even when the subject is feminine plural — les filles n'ont pas menti — the participle stays menti (no agreement). The verb is intransitive.
Common Mistakes
Mistake 1: Using être in compound tenses.
❌ Je suis menti.
Wrong — mentir takes avoir, not être.
✅ J'ai menti.
I lied.
Mistake 2: Using a direct object instead of à.
❌ Il a menti sa mère.
Wrong — mentir is intransitive; the recipient takes à.
✅ Il a menti à sa mère.
He lied to his mother.
Mistake 3: Confusing mentir with s'allonger / se coucher.
❌ Le chat ment sur le canapé.
Wrong verb — mentir is to deceive, not to recline.
✅ Le chat est allongé sur le canapé.
The cat is lying on the sofa.
Mistake 4: Trying to make the participle agree.
❌ Les filles ont mentie.
Wrong — mentir's participle menti is invariable, since there's no possible direct object.
✅ Les filles ont menti.
The girls lied.
Mistake 5: Forgetting consonant alternation in singular vs plural.
❌ Je ments / Il ments.
Wrong — singular drops the t: je mens, il ment.
✅ Je mens / Il ment / Nous mentons.
I lie / He lies / We lie.
Key takeaways
Mentir means to lie (tell falsehoods) and conjugates exactly like partir, sortir, dormir, sentir, servir — the partir family of irregular -ir verbs. The signature pattern: drop the consonant in the singular present (je mens, il ment), restore in the plural (nous mentons). The futur stem is the full infinitive mentir-. The participe passé menti is invariable because the verb is intransitive.
Auxiliary in compound tenses: avoir. Despite the moral weight, mentir is not in the maison d'être. J'ai menti, tu as menti, il a menti.
Constructions:
- mentir à quelqu'un (lie to someone)
- mentir sur quelque chose (lie about something)
- sans mentir (honestly, no exaggeration)
The compound démentir (to deny, refute) is high-frequency in news and journalism. Watch the English false friend: to lie in the sense of reclining is s'allonger / se coucher, never mentir.
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