主语补足语和同位语怎么区分

1、主语补足语，是对主语的补烫腥治奁充，使得句子更加完整。请看下面的例句：He was seen playing football yesterday.唁昼囫缍这句的含义是别人看见他正在踢足球。这里的playing football是主语he的补足语，故称作主语补足语。句首的主语就是主语补足语的逻辑主语。又比如：The book was thrown out of the window.那本书曾被扔出窗外。out of the window 是主语补足语。