An empty or unoccupied seat; a seat that is available.
空席にどうぞお座りください。
Please sit in an empty seat.
満員電車で空席はほとんどなかった。
On the crowded train there were hardly any empty seats.
空席の確保のため、早めに並んだ。
I lined up early to secure empty seats.
A vacancy; an unfilled position or post that requires filling.
部署に空席ができたので募集を開始する。
A vacancy has opened in the department, so we'll start recruiting.
議席の空席を埋めるための補欠選挙が行われる。
A by-election will be held to fill the vacant seat in the council.
役員の空席は内部昇格で埋められた。
The vacant executive position was filled by an internal promotion.