半助动词在功能上介于主动词和助动词之间，本身有词汇意义，可分为三类：a.以be为中心成分，如：be about to be going tobe bound to be able tobe due to be sure tob.以have为中心成分，如：had better/best have got tohave toc.以seem等为中心成分，如：seem to turn out to beappear to fail tohappen to tend to2.半助动词既可是限定形式（体现时态，语态特征），也可是非限定形式（不定式或现在分词）。半助动词后...
半系动词在功能上介于主动词和助动词之间，本身有词汇意义，可分为三类：a.以be为中心成分，如：be about to be going tobe bound to be able tobe due to be sure tob.以have为中心成分，如：had better/best have got to...
a.以be为中心成分，如：be about to be going tobe bound to be able tobe due to be sure tob.以have为中心成分，如：had better/best have got tohave toc.以seem等为中心成分，如：seem ...
