aboard: 在船(或飞机，车)上。如：I never went aboard a ship.
broad: 为形容词，宽广的。如：He has very broad shoulders.
abroad: 副词，在国外或海外。如：He often goes abroad.
board: 为动词，上(船，飞机，车)。如：The passengers are boarding the plane now.
asleep: 睡着,熟睡,只能做表语, The baby is asleep.
sleepy: 困的,有睡意的 I'm sleepy.
sleeping: 正在睡觉, a sleeping baby