» For the novel, see Clade (novel) A clade (from ancient Greek κλάδος, klados, "branch")'s a term used in modern alpha taxonomy, the scientific classification of living and fossil organisms, to describe a monophyletic group, defined as a group consisting of a single common ancestor and all its descendants. The common ancestor of any reasonably-sized group, and most of its descendants, will usually be long dead. It isn't necessary for a clade to contain any living… (More on Clade)