1. n. in psychoanalytic theory, the component of the personality that contains the instinctual, biological drives that supply the psyche with its basic energy or libido. Sigmund Freud conceived of the id as the most primitive component of the personality, located in the deepest level of the unconscious; it has no inner organization and operates in obedience to the pleasure principle. Thus, the infant’s life is dominated by the desire for immediate gratification of instincts, such as hunger and sex, until the ego begins to develop and operate in accordance with reality. See also primary process; structural model.

2. abbreviation for intradermal.