however(然而)

　　The text is difficult. It is ， however， not beyond the reach of the students.

　　At first the girl refused to go with him. Later， however， she changed her mind.

　　for(因为)

　　You’d better put on your coat， for it’s rather cold outside.

　　It must be snowing， for it is so bright outside.

　　The old man sat in front of the fire most of the day， for it was very cold

   but(但是)

　　“I won’t go. ” “But you’ve told me you would.”

　　“Can I help you?” “I’m afraid the box is too heavy for you， but thank you all the same.”

　　yet(然而)

　　They got to know each other a month ago， yet they have been in deep love now. (be in love 相爱)

　　She has her weaknesses， yet that doesn’t mean she is not qualified for the job.(be qualified for 胜任)

　　She is not a native speaker， yet her French is adequate for the job.(be adequate for 胜任)