名人教英文：冠词的不同用法 different ways of using articles
articles (冠词) refer to objects, either specifically or generally:
a. definite article "the" (定冠词) refers to objects specifically.
b. indefinite article "a" or "an" (不定冠词) refers to objects generally.
there are rules, and customary exceptions, governing their usage.
definite article 定冠词
definite articles are used in the following circumstances:
（a）the object to which the article refers is obvious or has been mentioned before. 定冠词所指定的名词是很明显或已经提过的
e.g. i bought a house. the house i bought is a big one.
（b）the object is unique. 所指的名词是独一无二的
e.g. the queen of england is visiting me.
（c）the object is a musical instrument or is limited to certain species. 用来指定乐器或其他某类事物
e.g. i am studying the piano and the human species.
（d）it refers to superlatives. 用来表示极级
e.g. you are the best! you are also the most diligent.
（e）it refers to oceans, waterways, ships, a collective class or a collection of states or mountain ranges.
用来指定某海洋、运河，总括类别如省、山脉等
e.g.i was on board the queen mary and noticed that unlike the alps or the himalayas or the suez canal, the united states of america borders on the pacific ocean.