Meanings
Usage patterns
〈場所〉に空きができるa vacancy/opening appears at a place
I heard a unit became vacant in that apartment building.
空き時間に〈動詞〉to do something during one's free time
I make a point of reading during my free time.
空きを見つけるto find an opening/vacancy
I found an open parking space.
空きがないthere is no room/vacancy
That hotel has no vacancies right now.
Expressions
空きを埋めるfill a gap; fill a vacancy; fill in a blank