Babylonian Talmud Shabbat 148a
Mishnah: A person may borrow bottles of wine or oil [on Shabbat], so long as he does not say to the lender, "Loan me . . ." This is also the case with a woman who borrows loaves of bread from her neighbor [on Shabbat].
Talmud: Rava b. Rav Hanan said to Abbaye, "What's the difference [if he says] 'Lend me . . . ' or 'Loan me?'" [Abbaye] said to him, "[If he says,] 'Lend me . . . ' [the lender] will not write down [the debt.] [If he says,] 'Loan me . . . ' [the lender] will write down [the debt]."
Another type of behavior that our Sages proscribed on Shabbat includes acts that may lead to Torah prohibitions. For example, we have seen that writing two letters (or a single word) is seen by the Mishnah as a Torah prohibition. Our Sages inherited a non-Torah prohibition on transacting business over Shabbat, lest one record the transaction in a ledger. (The prohibition on business can already be found in the Prophets and Writings. See for example, Isaiah 58:13, Amos 8:5, and Nehemiah 10:32.) However, our Sages remained aware that this prohibition was not of the same magnitude as Torah prohibitions and treated it with leniency.
In the above source we see examples of cases in which a kind of transaction is allowed by our Sages on Shabbat in order to further the pleasures of Shabbat. If one runs out of wine or challah or other food on Shabbat, or simply has forgotten to prepare these things before Shabbat, what can one do? One might look at any acquisition of foodstuffs as a transaction and simply forbid it. Our Sages did not take this approach. They made a distinction between formal and informal transactions. The former usually involves writing, the latter does not. Our Sages allow us to informally borrow the needed items to enhance our experience of Shabbat.
But how do we determine when the transaction is informal and friendly, and when it is formal and businesslike? Our Sages focused (I think, wisely) on the words spoken by the two parties engaged in the transaction. The words we use define the nature of our relationships and transactions in life. We negotiate our way in the world through the words we use. May we all use our words wisely on Shabbat and during the week.