一天yī tiān 1.一昼夜{a day}: ～二十四小时。{twenty-four hours a day} 2.一个白天{day}: ～一夜。{one day and one night} 3.泛指过去某一天{(in a broad sense) one day (in the past)}: ～,他谈起当演员的经过。{One day, he talked of how he became an actor.} 4.〈方dial.〉一天到晚。{whole day; all (the) day; from morning till night}