当直 (とうちょく)being on duty; being on watch; person on duty

being on duty; being on watchnoun (common) (futsuumeishi), noun or participle which takes the aux. verb suru
person on dutynoun (common) (futsuumeishi)

当直, its kanji, and other words that share them.Open this graph

Kanji in 当直

当初とうしょbeginning; start
当局とうきょくauthorities; relevant authorities
当時とうじat that time; in those days
当選とうせんbeing elected
当面とうめんcurrent; urgent
担当たんとうbeing in charge (of an area of responsibility); being responsible (for a work role, etc.)
本当ほんとうtruth; reality
当然とうぜんnatural; right
見直しみなおしreview; reconsideration
直前ちょくぜんjust before
直後ちょくごimmediately following
直接ちょくせつdirect; immediate
直じきsoon; in a moment
率直そっちょくfrank; candid
直ちにただちにat once; immediately
直面ちょくめんconfrontation

See how 当直 connects to the rest of Japanese.