① by and by表示“没多久,一会儿之后”,相当于soon或after a while。
By and by the school year will be over. 不多久这个学年就要结束了。
He'll be back by and by. 他一会儿就会回来了。
② by the by表示“顺便说到”,相当于incidentally,by the way。
By the by,what happened to the boy?顺便问一下,那个男孩后来怎样了?
③ by and large表示“大体上,基本上”。
By and large,the plan is practicable. 这个方案大体上可行。
④ gradually表示“渐渐地”,相当于slowly或little by little。
The baby is gradually learning to walk. 那个婴儿渐渐地开始学走路。