1.   probably是一个副词，意思是大概、也许、很可能。The White House probably won't make this plan public until July. 白宫可能要到7月份才会公布这项计划。

2.   还有几个表达相似含义的词，possibly, maybe 还有presumably 都有大概、或许的意思

3.   和probably的名词形式是 probability意思是可能性、几率。The probability of winning the lottery is really very low. 彩票的中奖几率是非常低的。