Tyrannosaurus rex

American  

[ti-ran-uh-sawr-uhs reks, tahy‐] / tɪˌræn əˈsɔr əs ˈreks, taɪ‐ /

Also T. rex

noun

1. tyrannosaur.

---

Tyrannosaurus rex Cultural  

1. A large, carnivorous (see carnivore) dinosaur that walked on two legs. Its name is from the Greek words meaning “tyrant” and “lizard” and the Latin word for “king.”

---

Usage

What is a Tyrannosaurus rex? Tyrannosaurus rex was a giant, meat-eating dinosaur that walked on two legs and had a long tail and a big head with sharp teeth (and, yes, two little arms). The name Tyrannosaurus rex comes from the Greek words tyranno (“tyrant”) and saurus (“lizard”) and the Latin word rex (“king”). So, Tyrannosaurus rex means something like “king of the tyrant lizards.” It is commonly called T. rex for short. The name is fitting: Tyrannosaurus rex is one of the largest land predators that has ever lived. It was the largest of the tyrannosaurs, reaching a length of 47 feet (14. 3 m) or more. People often list the T. rex as their favorite dinosaur, and its popularity has grown through many pop culture depictions, such as its appearances in the Jurassic Park series of movies and books. However, to be scientifically precise about it, the T. rex lived during the Late Cretaceous period, about 90–65 million years ago, around the end of the age of dinosaurs.

Etymology

Origin of Tyrannosaurus rex

First recorded in 1905–10; New Latin Tyrannosaurus, the genus name; see tyrannosaur ( def. ) + Latin rex “king”; see rex ( def. )

Example Sentences

Although Tyrannosaurus rex is the best known species in this group of dinosaurs, scientists continue to debate whether some fossils assigned to T. rex actually belong to closely related species.

From Science Daily • Mar. 5, 2026

The results provide a more complete portrait of Tyrannosaurus rex as a living animal, tracing its journey from young dinosaur to one of the largest land predators in Earth's history.

From Science Daily • Mar. 5, 2026

Scientists believe it rivalled the fearsome Tyrannosaurus rex in size, measuring around 40 feet long with a 20-inch sword-like crest on its head.

From Barron's • Feb. 27, 2026

For many years, paleontologists have debated whether the single skull used to define the species Nanotyrannus represented a true species or simply a young Tyrannosaurus rex.

From Science Daily • Dec. 9, 2025

After clearing that obstacle, Kyle quickly ducked left to escape the gaping jaws of a lunging Tyrannosaurus rex.

From "Mr. Lemoncello's Library Olympics" by Chris Grabenstein