空儿 (kòngr) is a noun that refers to either free / spare time (in the sense of a gap in one's schedule) or a physical space / room (an unoccupied area). It can also be extended to mean a chance or opportunity, especially in the expression 有/没有空儿 ('have / don't have the opportunity'). The word is always pronounced with a retroflex suffix (儿化), and is most commonly used after 有 or 没有. Unlike 空闲 (kòngxián) which focuses on the state of being idle, 空儿 emphasizes an available slot—in time or space.