有时，不同的比较结构可以表示相同的意思，因此，它们可以相互转换。
1. not as/ soas与lessthan的转换
The place was not as/ so crowded as it usually is yesterday.
The place was less crowded than it usually is yesterday.
昨天，这个地方不像平常那样挤满了人。
2. morethan与lessthan, not as/ soas的转换
Your picture is more beautiful than his.
His picture is less beautiful than yours.
His picture isnt as/ so beautiful as yours.
你的画比他的好看。
3.最高级与morethan, nomore than的转换
Math is the most difficult subject of all.
Math is more difficult than any other subject.
No subject is more difficult than math. 数学是所有学科中最难的。