The word "plate" is typically omitted in America and carpenters speak simply of the "sill".
In historic buildings the sills were almost always large, solid timbers framed together at the corners, carry the bents, and are set on the stone or brick foundation walls, piers, or piles (wood posts driven or set into the ground).
The sill typically carries the wall framing (posts and studs) and floor joists.
In automobiles, the sill plate is located underneath the door and sometimes displays the make or model of the vehicle.
In naval architecture, sill also refers to the lower horizontal plate (frame) height, above which doors and access opening are fixed.