Molecular evolution, the study of DNA and RNA sequence changes through time, has several synonyms that can be used interchangeably. Evolutionary genomics refers to the study of whole genomes and their evolution, while phylogenetics is the inference of evolutionary relationships between organisms based on molecular data. Other terms that are sometimes used include molecular phylogenetics, molecular systematics, and molecular genetics. While the terminology may vary, the field of molecular evolution is essential for understanding the processes that underlie the origin of species and the biodiversity we see today. By understanding how DNA and RNA sequences change over time, we can reconstruct the evolutionary history of life on Earth.