在《定冠詞省不得》一文里，談到了 5 個必須用定冠詞的例子。

定冠詞也出現在其他 11 種情況中，非同時注意不可。

⑴用在單數名詞前面，以代表同類的人或物，如：

● The ox is a useful animal for farmers.

● This type of work is easier for the teacher than for the student.

但當涉及 man 和 woman 這兩個名詞時，一般上不必用 the ：

● Man is mortal.

● Woman differs from man in many ways.

⑵用在單數名詞前面來表示有關名詞的抽象概念，如：

● Don’t play the fool.

● Peter is fond of the bottle.

⑶用在數目字前面，如：

● Mr Li is somewhere in the 30s.

● She was not yet born in the 50s.

⑷用在測量單位前面，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用在比較級形容詞或副詞之前，以加強其意義，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……”結構里，如：

● The more we practise, the more we improve.

● The better the staff, the better the performance.

⑺用在樂器名稱之前，如：

● The piano sounds better than the organ.

⑻用在劇院、電影院之前，如：

● Do you often go to the cinema?

● Tom went to the Lido last week.

⑼用在四個方向之前，如：

● The sun rises in the east and sets in the west.

⑽用在復數姓氏之前，以表示有關家人，如：

● The Browns will visit us tonight.

⑾用在某些慣用語之前，如：

● We know the ins and outs of the matter.

● Compare the pros and cons before you make your decision.