Fab

Fab is a term with several distinct meanings in different contexts. In everyday English, fab is a shortened form of fabulous and is used as slang to describe something excellent, stylish, or impressive. The term became popular in the 1960s and remains common in informal speech and media.

In immunology, Fab denotes the fragment antigen-binding region of an antibody. Fab fragments are generated by proteolytic cleavage (often with the enzyme papain) and consist of one constant and one variable domain from the heavy and light chains. They bind specifically to antigens and are used in research, diagnostics, and some therapies. The complementary fragment is Fc, the crystallizable fragment.

In popular culture, Fab is associated with the Beatles as the “Fab Four,” a nickname popularized by the media in the 1960s that remains a shorthand reference to the group.

In the semiconductor and electronics industries, fab is shorthand for fabrication facility or wafer fabrication plant, where integrated circuits are manufactured. The term is used to distinguish the manufacturing plant from design or testing facilities; a company may run multiple fabs around the world.

Other uses of FAB or fab include acronyms in organizations and standards, such as FAB as an abbreviation in corporate names or in technical literature. Context usually clarifies whether fab refers to slang, science, music, or manufacturing.