動(dòng)詞不定式省略to的情況：
（1）不定式在感觀動(dòng)詞（see,notice,look at,listen to,hear,watch,feel,observe）、使役動(dòng)詞（let,make,have）后作賓語補(bǔ)足語時(shí),通常省去to.如：
I have my students come early.
（2）不定式在help后作賓補(bǔ)時(shí),可帶to,也可省略to.如：
I helped him（to）find his lost watch.
注意：以上兩種情況變成被動(dòng)語態(tài)時(shí)要加上to.如：
She was seen to go into the classroom.
（3）如果兩個(gè)或多個(gè)不定式并列使用時(shí),常在第一個(gè)不定式前面加to,后面一般都省略.如：
To try and fail is better than not to try at all.
6.“疑問詞＋不定式”組成的不定式短語在句中可以作主語、賓語和表語.如：
She told me when to start.