To express the relationships that occur explicitly at the same time, the Italian language uses two important conjunctions: the most common one is certainly quando (when), immediately followed by mentre (while).
The latter, perhaps also due to its versatility – which we shall soon see – raises always several questions regarding its potential use; it is in any case one of the most common words in the current language, and it is important, for this reason, to have a good understanding of its origin and significance.
The etymology of mentre comes from the Latin expression dum interim which, with the old Italian pronunciation, merged into one term (let’s just think of the ancient forms domentre or dummentre). In Latin dum is an invariable element, which identifies the temporal context of the speech. Interim, in turn, consists of inter, which literally means “in the middle”, and im, meaning “that”.
Mentre could, therefore, be read as the abbreviated form of the expression “in that middle” to which is added a strong sense of time, which differentiates it from similar terms. The same etymological origin, in fact, is found in the word dentro, evolved from the expression ad interim. In this case, however, the preposition ad strongly indicates the spatial context and creates an important distinction between the words mentre and dentro.
The sequence was formerly phrased with the use of che (which), creating the form mentre che (while that), still in use today, although less and less frequently. Currently, this form is perfectly legal and accepted by the Italian language, but it is perceived as a literary variant or of typical use in a more regional context. The current language thus prefers the use of the simple form mentre compared to mentre che, as it sounds less ancient and popular.
The conjunction mentre can adopt different nuances. Its origin, as we have seen, is that of expressing the concept of simultaneity of a relation (eg. You must not distract yourself while you are studying), but it can take on other meanings. The concurrency can, in fact, be expressed also in the form of a well-defined duration, with the meaning of “per tutto il tempo in cui” (for all the time in which) replacing the conjunction finché (as long as). It is less and less frequent but still active [eg. Mentre io sarò qui non potrai parlare (for the period that I shall be here you will not be able to speak): with the meaning of “per tutto il tempo in cui sarò presente tu non potrai parlare” (during all the time that I will be present you will not be able to speak)].
The other important acceptation of mentre is given its adversarial use, where it can replace or strengthen the adverb invece. This use is strictly modern [(eg. Tutti lo accusano, mentre lui ha ragione (Everyone accuses him, while he is right)] and has no counterpart in the old Italian language that, instead, preferred expressions such as laddove (whereas).
A final use of this conjunction is of even more ancient origin (the first testimonies are present already in the fourteenth century) and is of a usage as a noun. It means that its role goes from being a functional tool of speech to expressing a separate entity in the speech itself. An example is: “Lo spettacolo era terminato e il pubblico applaudiva. In quel mentre, dietro le quinte, tutti stavano zitti” (The show was over and the audience was applauding. At that moment, behind the scenes, everyone was silent). The meaning here is that “nello stesso tempo” (at the same time) in which the audience applauds, behind the scenes everyone is silent.
Its use is once again perceived as very informal, but in the past had a very strong literary acceptation, offering a wonderfully graceful way of describing a time lapse in which a simultaneous relationship between two things taking place.