The best definition of a phylogenetic tree is as follows:
A phylogenetic tree is a graphical representation or diagram that depicts the evolutionary relationships and genetic connections between different organisms, species, or genes. It illustrates the branching patterns and common ancestry of these entities, providing insights into their evolutionary history and relatedness. The tree consists of branches, nodes, and tips, where the branches represent the evolutionary pathways, the nodes represent common ancestors, and the tips represent the present-day or extant species. It serves as a visual tool to understand the patterns and processes of evolution and to study the diversity and interrelationships of life on Earth.