noun

sill

SILL/sɪl/

A horizontal ledgelike support at the base of a structure.

The broad sill projects beneath the window's lower frame.

A close three-quarter view of a simple window, emphasizing the broad horizontal sill projecting beneath its lower frame.

Etymology

sillOld Englishbeam, threshold, foundation timber

Old English syll named a beam or timber forming a building’s base. That foundational sense narrowed to the bottom horizontal member of a window or doorway.

In context

The Sleepy Scientist 56:23

a cat stretched out on a window sill

The Sleepy Scientist | Dreams and the Sleeping Brain: What Science Knows So Far

More examples

The cat rests on the sill beneath the open window.
The builder replaces the rotted sills along the foundation.
Rainwater collects on the stone sill under the door.

Forms

sill · sills

windowsill noun — A ledge beneath a window opening.

Similar words

threshold: Specifically the strip or member across the bottom of a doorway.
ledge: Any narrow projecting shelf, not necessarily a structural base.