在《定冠词省不得》一文里，谈到了 5 个必须用定冠词的例子。

　　定冠词也出现在其他 11 种情况中，非同时注意不可。

　　⑴用在单数名词前面，以代表同类的人或物，如：
　　 ● The ox is a useful animal for farmers.
　　 ● This type of work is easier for the teacher than for the student.

　　但当涉及 man 和 woman 这两个名词时，一般上不必用 the ：
　　 ● Man is mortal.
　　 ● Woman differs from man in many ways.

　　⑵用在单数名词前面来表示有关名词的抽象概念，如：
　　 ● Don't play the fool.
　　 ● Peter is fond of the bottle.

　　⑶用在数目字前面，如：
　　 ● Mr Li is somewhere in the 30s.
　　 ● She was not yet born in the 50s.

　　⑷用在测量单位前面，以表示“每”（each/per），如：
　　 ● Some factory workers are paid by the hour.
　　 ● This car usually does 15 kilometres to the litre.

　　⑸用在比较级形容词或副词之前，以加强其意义，如：
　　 ● The teacher explained the idea again, but his students were none the wiser.
　　 ● Your mind will function all the better if you have some time away from your work.

　　⑹用在“the more/better……the more/better……”结构里，如：
　　 ● The more we practise, the more we improve.
　　 ● The better the staff, the better the performance.

　　⑺用在乐器名称之前，如：
　　 ● The piano sounds better than the organ.

　　⑻用在剧院、电影院之前，如：
　　 ● Do you often go to the cinema?
　　 ● Tom went to the Lido last week.

　　⑼用在四个方向之前，如：
　　 ● The sun rises in the east and sets in the west.

　　⑽用在复数姓氏之前，以表示有关家人，如：
　　 ● The Browns will visit us tonight.

　　⑾用在某些惯用语之前，如：
　　 ● We know the ins and outs of the matter.
　　 ● Compare the pros and cons before you make your decision.