What is "phylogenetic tree"

n. 1 (context sciences English) A graph illustrating evolutionary relationships among various entities (most often taxonomic groups) that are known to share a common ancestor. 2 (context biology English) A tree diagram that represents hypothesised phylogenetic (not tokogenetic) relationships between groups of organisms.

A phylogenetic tree or evolutionary tree is a branching diagram or " tree" showing the inferred evolutionary relationships among various biological species or other entities—their phylogeny—based upon similarities and differences in their physical or genetic characteristics. The taxa joined together in the tree are implied to have descended from a common ancestor. Phylogenetic trees are central to the field of phylogenetics.

In a phylogenetic tree, each node with descendants represents the inferred most recent common ancestor of the descendants, and the edge lengths in some trees may be interpreted as time estimates. Each node is called a taxonomic unit. Internal nodes are generally called hypothetical taxonomic units, as they cannot be directly observed. Trees are useful in fields of biology such as bioinformatics, systematics, and phylogenetic comparative methods.

Unrooted trees illustrate only the relatedness of the leaf nodes and do not require the ancestral root to be known or inferred.