Loanwords are words adopted by the speakers of one language from a different language (the source language). A loanword can also be called a borrowing. The abstract noun borrowing refers to the process of speakers adopting words from a source language into their native language. "Loan" and "borrowing" are of course metaphors, because there is no literal lending process. There is no transfer from one language to another, and no "returning" words to the source language. They simply come to be used by a speech community that speaks a different language from the one they originated in.