once用作連詞時(shí),意為“一旦……就……”,用于連接時(shí)間狀語從句,相當(dāng)于as soon as.如：
Once you start,you will never give up.一旦你開始了,你就不要放棄.
Once you begin to read it,you will like it.一旦你開始讀,你就會(huì)喜歡它.
Physics is easy to learn once you understand the rules.一旦你理解了規(guī)則,物理就不難學(xué)了.
注意：once引導(dǎo)的是時(shí)間狀語從句,從句要用一般現(xiàn)在時(shí)代替將來時(shí).