上空

overhead / in the sky

used in 上聲|上声[shang3 sheng1]

(bound form) up; upper; above; previous / first (of multiple parts) / to climb; to get onto; to go up / to attend (class or university) / (directional complement) up / (noun suffix) on; above

empty / air / sky / in vain

to empty / vacant / unoccupied / space / leisure / free time