T. rex is short for the dinosaur’s scientific name, Tyrannosaurus rex. Animals’ scientific names are written in a special format— the wider group, called a “genus” first, and then the species name that only describes that type of animal. All animals (and plants and fungi) have scientific names, but most of the animals alive today have common names that we use instead. For instance, a Grevy’s zebra is a specific kind of zebra, and its scientific name is Equus grevyi. Equus is like the animal’s last name—it applies to different members of the horse family, including zebras, donkeys, and domestic horses. Then the species name acts like the animal’s first name—“grevyi” (which means “Grevy’s”) is saying what kind of Equus, or horse, it is. The official rule for scientific names is that the genus name gets capitalized, the species name stays lowercase, and the whole name gets put in italics. To abbreviate an animal’s scientific name, you put a period after the genus and then put the species name—to shorten Equus grevyi, you would write E. grevyi.
Most dinosaurs don’t have common names like Grevy’s zebra—the only name they have is their scientific one. Lots of kinds of dinosaur groups are widely known by their genus names, like Stegosaurus and Triceratops. With Tyrannosaurus rex, we’re talking about this particular species within the Tyrannosaurus genus (scientists aren’t sure if there are any other species of Tyrannosaurus). But since that’s a little bit of a mouthful, we shorten Tyrannosaurus rex the same way we shorten all other scientific names—by putting a period after the genus and then using the species name. So, Tyrannosaurus rex becomes T. rex!
Photo by Zissoudisctrucker