Ontogeny (also ontogenesis or morphogenesis) is the origin and the development of an organism – for example: from the fertilized egg to mature form. It covers in essence, the study of an organism's lifespan. The word "ontogeny" comes from the Greek ὄντος, ontos, present participle singular of εἶναι, "to be"; and from the suffix -geny, which expresses the concept of "mode of production". In more general terms, ontogeny is defined as the history of structural change in a unity, which can be a cell, an organism, or a society of organisms, without the loss of the organization which allows that unity to exist.
Ontogeny in psychoanalysis
Ontogenesis in a psychoanalytical context is the development of the whole organism, viewed from the light of occurrences during the life, not in the last place in the pre-history of early childhood, which has become unconscious, according to Sigmund Freud. After the possibilities of ontogenesis have been exhausted, phylogenesis might be explanatory of the development of a neurosis.