對比原則
　　She is usually prompt for all her classes, but today she arrived in the middle of her first class。
　　but表示意思的轉折,，因此可以看出but前后的意思是相反的,。后半句說，她今天在第一節(jié)課上了一半時才來,。反推回去,，她平時應該是一向“準時”的了,。
　　The pain on the cottage had peeled in a few places, otherwise they looked well kept。
　　句中peel可從otherwise后面的對比猜出是“脫落”之意,。

　　說明原則
　　Ann is very smart. She always knows the answers to all the teachers’questions,。
　　第二句是對前一句的補充說明。一個能回答老師所有問題的女孩,，Ann一定是很“聰明”的,。

　　Capacitance, or the ability to store electric charge, is one of the most common characteristics of electronic circuits。
　　由后半句的解釋我們很快猜出生詞capacitance詞義——電容量,。

　　順序原則
　　After Ms Ellis put the letters in the envelope, she sealed it and put a stamp on it,。
　　在發(fā)信時，先把信裝入信封,，封上口,，然后貼上郵票，是合理的順序,，通過前后動作,，不難看出seal是“封口”的意思。

　　接下來我們再做個練習,，請看下面的文段：
　　After we had travelled for about twenty miles, there was still no sign of the town which was marked on the map. We were beginning to get worried. Then, without warning, the car stopped. A quick examination showed that we had run out of petrol. Although we had little food with us, only a few biscuits and some chocolate, we decided to spend the night in the car,。
　　這一段中，假設petrol和biscuit兩個詞是生詞,，但我們可以從句子的前后文中推斷出這兩個詞的意思,。如文中提到汽車在沒有任何出毛病的先兆時就突然停了，文中又有run our of——“用完”這個詞組,，因此可以推斷出一定是汽油用完了,，從而petrol的意思即可推測出。下邊的biscuit是生詞,，但這一句的前半句提到了 we had little food with us, biscuit和chocolate都是進一步補充說明是什么樣的food,，由此可見，這兩樣東西是“食品”,。這時我們已經(jīng)明白了大致的意思,，不查詞典，也不妨礙我們理解文章的意思,。因此,，就可以繼續(xù)讀下去，有時讀到后面,，又會發(fā)現(xiàn)前面出現(xiàn)的生詞的意思在后面有了解釋,。（智慧校園大學）