英语的虚词(form word),也称结构词(structural word)或功能词(function word),包括冠词、介词、助动词、并列连接词(coordinator)和从属连接词(subordinator)等,英语虚词都是与实词(notion word / full word)相对而言的,在句中主要起辅助和连接等作用。
功能词又叫结构词或虚词,指没有完整词汇意义,但是有语法意义或语法功能的词,常见的有代词、数词、冠词、助动词和情态动词,少数副词、介词、连词和感叹词,其数量比较的少,如 举例 for example, such as , 对比 while, and, instead, meanwhile,转折 but , while, however,因果 so, for, because, since, due to, because of,总结 in a word, in a conclusion, all in all,列举first, next , what's more, besides, in addition ……------精锐成山校区