in caseif 如果；若*In case he arrives be fore I get back，please ask him to wait．如果 我回来前他就到了，请叫他等我。*In case it rains，do not expect me． 如果天下雨，就不要指望我来了。*in case of in the event of； as for要是；在… 时（候）In case of fire，the ...
onceonce[wʌns; wʌns]《one 的中古英语所有格副词用法》副词1 一次,一遍,一倍~ a day一天一次~ more= ~ again再 （来） 一次~ or twice一两次I have ~ skated.我曾溜过冰O~ one is one.一乘一等于一2 一次也 （没有…）I haven't seen him ~.我一次也没见 ...