Glossary

Hyoid apparatus

The chain of small bones and ligaments supporting the tongue and larynx, whose structure helps explain why some cats roar and others purr.

Also called: hyoid bone, roar versus purr, why big cats roar

The hyoid apparatus is a set of small bones and ligaments that holds the tongue root and the voice box, or larynx, in place. It sits in the throat and attaches to the skull. In cats, differences in this structure were once used to sort species into roarers and purrers.

In the lion, tiger, leopard and jaguar, the lower part of the hyoid is joined by an elastic ligament, rather than bone, which was thought to let the larynx move and produce a deep roar. In cats such as the cheetah, cougar and domestic cat, the hyoid is fully bony, and these species purr. Roaring and purring were long described as mutually exclusive. Newer work shows the shape and tissue of the larynx and vocal folds matter too. The snow leopard shows the hyoid alone does not decide the question, since it has the flexible ligament yet does not roar.

Domestic cats purr on both the in-breath and the out-breath, using muscles in the larynx. Purring usually signals contentment, but cats may also purr when frightened or in pain, so context matters. A cat that stops eating or hides while purring should be checked by a vet.

Last reviewed November 7, 2026

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Related terms

Big cat An informal name for the largest wild cats, usually the lion, tiger, leopard and jaguar, and often the snow leopard, cheetah and cougar too. Felid Any member of the cat family, Felidae, from the house cat to the tiger, and including extinct cats such as the sabre-toothed cats. Black panther A popular name for a black leopard in Asia and Africa or a black jaguar in the Americas; there is no species of that name. Apex predator An animal at the top of its food chain that adults of the species hunt and that has no natural predators of its own. Camera trap A motion-triggered camera left in the field that photographs passing animals, widely used to count shy wild cats such as tigers and jaguars.

Related guides

Why cats purr Why cats purr, how the sound is made, the different kinds of purr, what it can mean besides contentment, and when a purring cat still needs a vet.