The Shulhan Aruch (Orah Haim 307:11; listen to audio recording for precise citation) codifies an interesting Halacha relevant to borrowing objects on Shabbat. He writes that if a person wants to borrow his fellow’s object on Shabbat, he must use the word "Hash’ileni," rather than "Halveni." These two Hebrew words both mean "lend to me," but whereas "Halveni" has a connotation of long-term borrowing, "Hash’ileni" is generally used in reference to borrowing for a short period of time. One should not speak of long-term borrowing on Shabbat – for a duration of one month or more – because the parties might end up writing some kind of note as proof of the lending, in violation of Shabbat. Therefore, the Shulhan Aruch writes, one who borrows on Shabbat must ensure to formulate his request with the term "Hash’ileni," rather than "Halveni."
But what if a person expresses his request in English, in which the same term – "lend" or "borrow" – is used in reference to both long-term and short-term borrowing?
The Shulhan Aruch writes that one who uses a language that uses the same term for both kinds of borrowing must avoid mentioning "borrowing" or "lending" when he asks to borrow something on Shabbat, and must instead say, "Please give me the object." The Mishna Berura (commentary by Rav Yisrael Meir Kagan of Radin, 1839-1933) clarifies that one may say, "Please give this to me and I will give it back to you." One must, however, avoid using the term "borrow" or "lend."
This Halacha is very applicable. If, for example, a person wishes to borrow his neighbor’s Siddur (assuming, of course, there is a proper Erub), he should ensure not to ask to "borrow" the Siddur, but rather to ask if he could have the Siddur for a period of time.
It should be noted that one may not ask on Shabbat to borrow something after Shabbat. It is forbidden to speak on Shabbat of one’s plans for after Shabbat, and therefore one should not request on Shabbat to borrow something after Shabbat.
Summary: If one borrows something from his fellow on Shabbat, he should avoid using the words "borrow" and "lend" when formulating his request, and should instead ask if he could have the object for the period of time in question.
