1. perhaps, maybe是副词，用来修饰句子，用在句子开头表示“或许”的意思，比如 Perhaps he will forgive you,或者Maybe this is the best choice.2. may be则是情态动词+be动词，用作句子的谓语,表示“或许是”，比如 He may be the one who broke the window.3. possible则是个形容词，象一般形容词一样，可以修饰名词，如possible solution,或者用在be动词后作状语，如 Everything is possible...
