According to Lynne M. Clos of Fossil News, a derived character is an advanced trait that only appears in some members of an evolutionary group. An example of a derived character is the loss of a tail, a trait that first appeared in an ancestor of apes and man.
Derived characters are part of a branch of evolutionary biology called cladistics, which Fossil News defines as a method of analyzing the evolutionary relationships between groups to construct their family tree. It is based on the classification of organisms according to their evolutionary relationships. Evolutionary biologists discover these relationships by analyzing the primitive and derived characters of organisms. All members of an evolutionary group possess primitive characters, while only some members possess derived characters.
According to Understanding Evolution, biologists use biological evidence to form a hypothesis about how organisms are related called a phylogeny. They build phylogenetic trees, which are family trees that represent patterns of ancestry. Shared derived characters, traits that advanced members of two lineages have in common, help biologists place organisms into less and less inclusive groups. For example, the trait of having four limbs is a derived character shared at one point in history by amphibians, turtles, lizards, snakes, crocodiles, birds and mammals. Having four limbs helps group these vertebrates together in a clade.