From Proto-Italic *mentjōr, denominal verb from mēns, mentis (“mind”). Further from Proto-Indo-European *méntis, from *men-. The meaning "to lie" stems from a semantic shift "to be inventive, have second thoughts" > "to lie, conjure up". Compare comminīscor, commentum also from this root and again with these meanings. Further compare cognate Russian мни́мый (mnímyj), сомни́тельный (somnítelʹnyj).
Also compare typologically Russian вы́мысел (výmysel) (akin to мысль (myslʹ)).
mentior (present infinitive mentīrī or mentīrier, perfect active mentītus sum); fourth conjugation, deponent
| indicative | singular | plural | |||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| first | second | third | first | second | third | ||||||||
| active | present | mentior | mentīris, mentīre |
mentītur | mentīmur | mentīminī | mentiuntur | ||||||
| imperfect | mentiēbar | mentiēbāris, mentiēbāre |
mentiēbātur | mentiēbāmur | mentiēbāminī | mentiēbantur | |||||||
| future | mentiar | mentiēris, mentiēre |
mentiētur | mentiēmur | mentiēminī | mentientur | |||||||
| perfect | mentītus + present active indicative of sum | ||||||||||||
| pluperfect | mentītus + imperfect active indicative of sum | ||||||||||||
| future perfect | mentītus + future active indicative of sum | ||||||||||||
| subjunctive | singular | plural | |||||||||||
| first | second | third | first | second | third | ||||||||
| active | present | mentiar | mentiāris, mentiāre |
mentiātur | mentiāmur | mentiāminī | mentiantur | ||||||
| imperfect | mentīrer | mentīrēris, mentīrēre |
mentīrētur | mentīrēmur | mentīrēminī | mentīrentur | |||||||
| perfect | mentītus + present active subjunctive of sum | ||||||||||||
| pluperfect | mentītus + imperfect active subjunctive of sum | ||||||||||||
| imperative | singular | plural | |||||||||||
| first | second | third | first | second | third | ||||||||
| active | present | — | mentīre | — | — | mentīminī | — | ||||||
| future | — | mentītor | mentītor | — | — | mentiuntor | |||||||
| non-finite forms | infinitive | participle | |||||||||||
| active | passive | active | passive | ||||||||||
| present | mentīrī, mentīrier1 |
— | mentiēns | — | |||||||||
| future | mentītūrum esse | — | mentītūrus | mentiendus, mentiundus | |||||||||
| perfect | mentītum esse | — | mentītus | — | |||||||||
| future perfect | mentītum fore | — | — | — | |||||||||
| perfect potential | mentītūrum fuisse | — | — | — | |||||||||
| verbal nouns | gerund | supine | |||||||||||
| genitive | dative | accusative | ablative | accusative | ablative | ||||||||
| mentiendī | mentiendō | mentiendum | mentiendō | mentītum | mentītū | ||||||||
1The present passive infinitive in -ier is a rare poetic form which is attested.