id

Id is a term with multiple meanings across disciplines, including psychology, linguistics, and information technology. In everyday usage, it is also an abbreviation for identity or identification. The different senses are distinct but share a common idea of a fundamental unit of behavior, meaning, or labeling.

In psychology, the id is a central element of Sigmund Freud's structural model of the mind. It represents the primitive, instinctual drives and impulses present from birth, operating on the pleasure principle and seeking immediate gratification. The id is unconscious and amoral, serving as a repository for basic desires such as hunger, sex, and aggression. Its impulses are balanced by the ego, which mediates reality, and the superego, which imposes moral norms. Together, these elements shape human behavior.

In linguistics and classical languages, id is a neuter demonstrative pronoun in Latin meaning “that” or “it.” In English, the term id more commonly appears in abbreviated form as ID, denoting identification or identity.

In computing and information technology, ID stands for identifier. An identifier is a unique label assigned to an entity such as a user, a record in a database, or an element in a document. In web development, the id attribute assigns a unique identifier to an HTML element for styling and scripting. In mathematics and computer science, the identity function id maps every input to itself, i.e., id(x) = x.

Overall, id serves as a compact label for a fundamental element—whether a psychic impulse, a linguistic reference, or a unique tag in data systems.