Plain English Meaning

Microscopic hairs growing out of sensing cells in your inner ear. When fluid in the inner ear moves, the hairs bend, and that bending tells your brain which way your head is moving or tilting.

Full Definition

Tiny hair-like projections that extend from specialised sensory cells inside the inner ear. These projections sit in fluid within the semicircular canals and the vestibule, and they bend when the fluid moves. The bending generates nerve signals that the brain interprets as motion or position of the head.

Context Anchor

Seen in instrument flying discussions about the inner ear, balance, and why a pilot can feel motion that does not match what the flight instruments show.

Derivation

Filament comes from the Latin filum, meaning 'thread.' The word is used here in its literal sense: the projections are thread-like in shape. Knowing this helps you picture them as fine threads that bend, rather than as anything more complicated.