Adultery is a word used in religious texts like Exodus 20:14. It applies to a married person sleeping with someone other than the person who they are married to. Adultery usually comes with a heavy punishment for example, death by stoning in some Muslim countries. In most countries adultery is no longer a crime, but most people still see it as a bad thing.(see Gospel of John 8) If a person who is married takes part in adultery, that person's husband or wife would usually have the right to be able to go to court to divorce them.
The word adultery originates not from “adult”, as is commonly thought in English-speaking countries, but from the Late Latin word for “to alter, corrupt”: “adulterare”. “Adulterare” in turn is formed by the combination of “ad” (towards), and “alter” (other), together with the infinitive form “are” (making it a verb). Thus the meaning is literally “to make other”. In contrast, the word “adult” (meaning a person of mature years) comes from another Latin root, “adolescere”, meaning to grow up or mature: a combination of “ad” (towards), “alere” (to nourish, to grow), and the inchoative infix “sc”(meaning to enter into a state of).