only then ，是过一小会儿的意思，一般用在句首，引导倒装句.
例句Only then did he realize the importance of English．
解析：在句首的only如果后面跟了副词、介词短语或从句等状语，则主句用倒装结构.如only后跟的是主语，就不用倒装结构了.
1、Only then did she realize the stress he was under.直到那时她才意识到他所承受的压力。
2、Only then did I learn the unpalatable truth.直到那时我才得知令人难以接受的真相。
3、It was only then that I began to learn the unpalatable truth about John.直到那时我才开始了解到有关约翰的一些令人难以接受的实情。
