Jocelyn's answer is very good. Here's my answer: Perhaps means maybe. Maybe means perhaps. How do you like my answer so far? :) Maybe and perhaps are synonyms. Both mean that there is a chance (something is possible / could happen / might happen). 'Probably' means that there is a high or low chance that something will happen or will be true or ... Probabilities can be calculated mathematically. For example - What is the probability that A, B or C will happen? Probability of A happening = 10% (0.10) Probability of B happening = 11% (0.11) Probability of C happening = 79% (0.79) So we can say that C has the highest probability of happening. In English, when we talk about tomorrow's weather we talk about the probability of precipitation (rain or snow) (POP/PoP). It is usually expressed (written or spoken) (expressed means described) in mathematical terms, e.g. There is an X% probability (or chance) that it will rain tomorrow. I can't believe it - I actually remembered something from all those math classes I took many years ago :)

Maybe can be used alone or in the beginning of the sentence. 'Are you gonna visit me tomorrow?' 'Maybe!' . And maybe means an uncertain reply, lets say only 50% probability of visiting the person. Perhaps and Probably seem like the probability is a little bit more than 50%. Am I correct???