1.冠词指不定冠词a,an和定冠词the2.不定冠词an常用于元音发音开头的词前,如：an hour,an English car. 请区别：a useful machine3.指上文提到过的人或物,用定冠词the4.在世界上独一无二的事物前用定冠词the.如：the ...