Clade

From Freepedia

A clade is group of organisms which share a common ancestor and which includes all decendents of that ancestor. Taxonomy which requires all taxa to be clades is called cladistics. A clade may or may not conform to an existing taxon. A clade is thus a monophyletic group of organisms. The term evolutionary grade is sometimes used for groups of related organisms that don't include all decendents of their common ancestor.

The PhyloCode is an attempt at a Code that will allow clades to get a formal name.