One of the definitions is The act of distinguishing or describing a thing, by giving its different, or specific difference; exact definition or determination.
Another one would be The gradual formation or production of organs or parts by a process of evolution or development, as when the seed develops the root and the stem, the initial stem develops the leaf, branches, and flower buds; or in animal life, when the germ evolves the digestive and other organs and members, or when the animals as they advance in organization acquire special organs for specific purposes.