Or, "from the outset", referring to an inquiry or investigation. In literature, it refers to a story told from the beginning rather than "in medias res" ("from the middle"). In law, it refers to a thing being true from its beginning or from the instant of the act, rather than from when the court declared it so. An annulment is a judicial declaration of the invalidity or nullity of a marriage ab initio; i. e., that the pseudo marriage was "no thing" (in Latin, "nullius", from which the word "nullity" derives) and never existed, except perhaps in name only. In science, the phrase refers to the first principles. In other contexts, it often refers to beginner or training courses. "Ab initio mundi" means "from the beginning of the world".