【導語】英語語法讓很多學生都頭疼，因為複雜難懂的句式和片語有時難以記憶。本章主要介紹英語語法中的句子成分，希望對同學們的英語語法學習有所幫助。
1. be動詞的否定式
be 動詞根據不同的'人稱和時態有不同的形式，在一般現在時中是am , is , are可用作聯絡動詞，構成否定式時，一律在其後面加否定詞not.
He is reading. --- He is not reading. They are from China. --- They are not from China.
2. 情態動詞的否定式
情態動詞的否定式是在其後面直接加not. 如：
I can swim. --- I cant swim. He can dance. --- He cant dance. You should go to school at seven. --- You shouldnt go to school at seven.
3. 實義動詞的否定句
實義動詞變否定句時，要藉助助動詞do , does，在一般現在時中用do或者does其句子結構為：主語+ dont / doesnt + 動詞原形+其它 例如：
I like pop music. --- I dont like pop music. He likes running. --- He doesnt like running.
She does her homework at home. --- She doesnt do her homework at home
