probable 是形容词,probably 是副词,
1.他很可能是忘了.It is probable that he forgot.
2.他或许没听懂我的话.Probably,he didn’t catch my meaning.
probable只能用在It is probable that的句型中,而不能说We are probable to do sth.
误译：We are probable to make mistakes when we learn English.
正译：1.It is probable/Likely that we will make mistakes when we learn English.