塵入[gomiire] trashcan
塵箱[gomibako] garbage can
黄塵[koujin] dust (in air)
灰塵[haijin] ashes and dust
含塵率[ganjinritsu] dust content

吸塵[kyuujin] dust vacuuming
後塵[koujin] second fiddle
市塵[shijin] city dust
塵芥[jinkai] rubbish

医界[ikai] medical world
医学界[igakukai] medical world
黄金世界[ougonsekai] utopia
下界[gekai] this world
花柳界[karyuukai] red-light district

界隈[kaiwai] neighborhood
界面[kaimen] interface
各界[kakkai] each field
学界[gakkai] academic or scientific world
官界[kankai] bureaucracy