表并列或递进: and, both…and, neither…nor, not only…but also;

表选择:or, either…or;

表转折或让步:but, although, though, however, even though, in spite of, on the contrary;

表对比:like, unlike, while;

表举例:for example, such as, that’s to say;

表强调:in fact, of course, besides;

表时间顺序:when, after, before, as soon as, soon after;

表因果关系:because, since, as, for, for this reason，as a result;

表结论:in a word, to sum up. In summary, in conclusion, on the whole;