请问英文to be的用法

这是be动词的不定式。一般会在它后面加上名词或形容词构成动词不定式短语,在句中可作主语,宾语,表语,定语,状语。
例如：
1。To be a doctor is his dream。(主语)
2。I want to be a teacher。(宾语)
3。His job is to be a waitor。(表语)
4。The meeting to be held tomorrow is important。(定语)
5 To be a doctor,you must be patient。（状语)