You use surely, especially in BrE, to show that you are almost certain about what you are saying and you want other people to agree with you. * surely 表示对所说的话几乎肯定无疑，并希望别人同意自己的看法，尤用于英式英语：◆Surely this can't be right?这不可能是对的吧？Surely in negative sentences shows that something surprises you and you do not want to believe it.在否定句中，surely 表示某事使人感到吃惊而不愿相信：◆You're surely not thinking of going, are you?你不是想走吧？
Certainly usually means 'without doubt' or 'definitely', and is used to show that you strongly believe something or to emphasize that something is really true. * certainly 常指无疑地、确定地，用以表示坚信某事或强调某事属实：◆I'll certainly remember this trip!我绝不会忘记这次旅行！In informal NAmE this would be非正式的美式英语说法为：◆I'll sure remember this trip!我绝不会忘记这次旅行！
Compare比较：◆The meal was certainly too expensive(= there is no doubt about it).这顿饭的确太贵了（毫无疑问）。and和：◆The meal was surely too expensive?(= that is my opinion. Don't you agree?)这顿饭太贵了吧？（我这样认为，你不这样认为吗？）
In formal language only, surely can be used to mean 'without doubt'.只有在正式用语中，surely 才表示无疑：◆This will surely end in disaster.这无疑将以灾难告终。
