adv.立刻；機會難得
機不可失；時不再來；勿失良機
例句
1.What are we waiting for? It's now or never .
我們到底在等待什麽？現在，或者從未如此。
2.You've got to ask her. It's now or never.
妳得去問她，立刻就去，否則沒機會了。
3.Perhaps you may want to "now or never" , since it has been lost, how could catching back?
可能妳會想“機不可失，時不再來”，既然已經失去了，怎麽可能再追得回來？
4.You've got to ask him. It's now or never.
妳得去問他，馬上去否則就沒機會了。
5.Enraged, Craig gives his son an ultimatum to go home with him now or never return.
盛怒的克雷格向兒子發出最後通牒，要麽跟他馬上回家，要麽永遠都不要回來。