想必 presumably; most probably [likely]: 想必如此 think it must be so; 他没有回信, 想必没有收到我的信。 no reply from him yet; presumably he hasn't received my letter
大概 1.(大致内容或情况) general idea; broad outline 只知道个大概 have only a general idea2.(大约) general; rough; approximate 大概的估计 a rough estimate; 大概的数字 an approximate figure; 大概的分析 a general analysis3.(可能) probably; most likely; presumably 我下个月大概还要来这儿。 i shall very likely be here again next month