Why Is It Called “Adultery” When It’s Not A Particularly “Adult” Thing To Do? Our society’s constant obsession with relationships and especially celebrity marriages—with their ups and downs, and often very salacious details—can lead us to wonder and ask big questions about the words we use to talk about love, commitment, and desire. While this isn’t People magazine or “Dear Abby,” perhaps we can use our natural curiosity as an excuse to look at a dilemma of language that is as enigmatic as the state of marriage itself: the complexities of adult and adultery. How can such similar words have such different meanings? Two words from different roots Remarkably, the answer is that the words don’t share a common ancestor. Adult comes from the Latin verb adolescere, “to grow up, mature.” Adultery, on the other hand, derives from the Old French word, avoutrie, which in turn evolved from a distinct Latin verb, adulterare, “to corrupt.” The verb adulterate, “to debase or make impure by adding inferior materials or elements,” stems from the same source. The sense of adult that means “pornographic” emerged as a kind of reverse assumption that adult and adultery have more direct links than they do. The two types of adultery Let’s look at the dictionary definition of adultery: “voluntary sexual intercourse between a married person and someone other than his or her lawful spouse.” In fact, there are two types: single adultery (with an unmarried person) and double adultery (with a married person.) Here is the definition of adult: “having attained full size and strength; grown up; mature.” What conclusions can we draw regarding relationships from these twists of etymology? Maybe that a real-life definition of adult is the condition of being responsible for our choices, and that the choice of whom to love and honor is probably the most adult decision of all. Looking for more word facts? Check out the history behind the word achoo!