The influence of English, or more precisely of Anglo-American, on the Italian language is very strong today. That has led to the increasingly frequent problem of what form to use when certain Anglicisms are used in the plural. In English, the plural of nouns is formed, in general, by adding -s or -es; for example film-films, leader-leaders, flash-flashes, hobby-hobbies. But in Italian the tendency is to keep the same form in the plural as in the singular: il film—i film, il leader—i leaders, il flash—i flash, il hobby—gli hobby. This is only a general guideline; many Italian newspapers frequently waiver between i leader and i leaders, gli hobby and gli hobbies.
However, grammar books and dictionaries are somewhat in agreement in recommending retaining the singular form for the plural; it is correct and acceptable in Italian to write and say il bar—i bar, lo sport—gli sport, and la star—le star. This formula is based on the following reasoning: in the Italian language there is no final -s to indicate the plural; instead the invariable plural exists in such old and new words as la città—le città, la diagnosi—le diagnosi, radio—radio, la serie—le serie, la virtù—le virtù. In fact, it is preferable to imitate a model already part of the structure of Italian, rather than introduce another (the final -s of English) that is completely foreign.
There are, however, those who think differently. According to some linguists, Anglicisms that entered Italian a long time ago should have an unchanged plural (il bar—i bar, il film—i film, lo sport—gli sport); while more recent and less common Anglicisms should retain the plural of the language of origin (the same argument is made for Frenchified words). But the boundary between the two groups of words is uncertain and unstable; so for example, if in the Sixties the word test was not yet well known, today instead it is widespread. To adhere to this suggested rule, i tests would have been the preferred form, both written and spoken, in the Sixties, and then instead revert to the form with the unchanged plural i test.
This standard, though, risks uncertainty, and above all it would be very difficult to apply in a systematic way, partly because of the many exceptions that English has in the formation of the plural: think of the anomolous plurals man-men, mouse-mice, roof-rooves, or foot-feet. Anglicisms such as quiz or sit-in pose the risk of seeming incomprehensible or unfamiliar to many Italians if used in the form of the English plural: quizzes, sit-ins. Nevertheless, there are foreign words that have entered the Italian lexicon directly in the plural form, such as jeans (already defective in the singular in English, like pants), so that the plurals are sometimes misused as a singular.
Therefore, the plural of Anglicisms that have entered unchanged in Italian seems to be the easier and more advisable rule, at least in general. However, a different option, which tends to conform to the conventional form of the English plural, can sometimes be justified by the specific situation: in the case, for example, of a scientific or specialist text, in which technical Anglicisms appear that are unfamiliar in the common language.