Plain English Meaning

A tiny sac inside the inner ear that helps you sense whether you are moving up or down and how your head is tilted compared to gravity.

Full Definition

A small fluid-filled sac in the inner ear, part of the vestibular system, that detects linear acceleration and head position relative to gravity along the vertical axis. Working together with the utricle, the saccule senses up-and-down motion and tilt by means of tiny hair cells topped with calcium carbonate crystals (otoliths) that shift with movement.

Context Anchor

Seen in instrument flying discussions of the ear, balance, and spatial disorientation.

Derivation

From the Latin sacculus, meaning 'little sac' or 'small bag.' The name describes its physical shape — a tiny pouch inside the inner ear.