Emphatic Double Negative Sentence 强调型双重否定句
Euphemistic Double Negative Sentence 委婉型双重否定句 ; 重否定句
Affirmative Double Negative Sentence 肯定型双重否定句
As a kind of marked negation, metalinguistic negation is usually marked by the double-sentence structure, consisting of a basic negative sentence plus another positive or negative sentence.
元语否定作为一种标记否定，它的标记形式一般为由本句和义句构成的复句结构式。
You cannot have a negative sentence after unless because that would make the sentence a double negative and senseless.
在unless之后不能接否定句，因为这就造成了双重否定，句子没有意义。
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