补足语不属于定语，定语是起限定或修饰的作用的，补足语则是对主语或宾语做解释说明的
主语补足语必须出现在被动语态的句子里，主补其实是被动语态的宾补
如: They caught the boy stealing. （stealing 作为宾语补足语）
转化为被动语态The boy was caught stealing. （stealing转化为主语补足语)
被动语态的主语补足语与主动语态的宾语补足语是密切相关的。例如：
(1) I saw him playing basketball yesterday.
(2) He was seen playing basketball yesterday.
在句子中修饰限制名词或代词的成分是定语。
如: We love our country
名词前的“our”就是名词“country”的定语
