英语通过不置于句首的成分被置于句首作主位 ,主位与主语不重叠 ,这样的主位就是有标记主位。英语语法倒装的主位与有标记主位不同 ,前者是强制性的 ,后者是选择性的。选用有标记主位与句子需表达的某种修辞效果有关。 English is placed at the beginning of the sentence as the theme of the text through the elements that are not placed at the beginning of the sentence. The theme does not overlap with the subject. Such a theme is marked with the theme. The theme of English grammar flipping is different from the marked theme. The former is mandatory and the latter is selective. The choice of the subject of the mark has something to do with the rhetorical effect that the sentence needs to express.