Biologically, an adult is a human being or other organism that has reached sexual maturity. In human context, the term adult additionally has meanings associated with social and legal concepts. In contrast to a "minor", a legal adult is a person who has attained the age of majority and is therefore regarded as independent, self-sufficient, and . Human adulthood encompasses psychological adult development. Definitions of adulthood are often inconsistent and contradictory; a person may be biologically an adult, and have adult behavior but still be treated as a child if they are under the legal age of majority. Conversely, one may legally be an adult but possess none of the maturity and responsibility that may define an adult character.

Adult (stylized as ADULT.) is an American band from Detroit, Michigan, formed in 1998. The band integrates vocals with drum machines, analog synthesizers and electronic/punk elements. While popular in their home city of Detroit, they are also very popular in Germany and the United Kingdom.

ICM Registry operates the .xxx (pronounced "dot triple-X") sponsored top-level domain (sTLD) registry, which is designed for pornography. The ICM Registry operates from Palm Beach Gardens, Florida. It is owned by Stuart Lawley.

Pornographic magazines, sometimes known as adult, sex or top-shelf magazines, are magazines that contain content of an explicitly sexual nature. Publications of this kind may contain images of attractive naked subjects, as is the case in softcore pornography, and, in the usual case of hardcore pornography, depictions of masturbation, oral or anal sex, or intercourse.