In psychoanalysis, the first libidinal stage of psychosexual development, occupying the first year of life, during which libido is focused on the mouth and lips, as they are stimulated during feeding, through which the object-relationship is expressed, the loving relationship towards the mother being experienced through ideas of eating and being eaten. During this stage, the instinctual source is the oral zone, the instinctual object is food, and the instinctual aim is incorporation. Sigmund Freud (1856–1939) had not developed this concept when the first edition of his book Three Essays on the Theory of Sexuality appeared in 1905, but the revised edition of 1915 included a full and detailed exposition of the theory. See early oral phase, oral sadistic phase. See also anal stage, genital stage, latency period, oral-aggressive character, oral character, phallic stage, polymorphous perversity. Also called the oral phase.