副詞 for certain:

1. definitely or positively (`sure' is sometimes used informally for `surely')
   同義詞：surely, certainly, sure, for sure, sure enough, sure as shooting

1. I don't yet know for certain.
   我知道得不確切。
2. I couldn't say for certain when he'll arrive.
   我說(shuō)不準(zhǔn)他什麼時(shí)候到。
3. For certain reasons I will be unable to attend the meeting.
   因?yàn)槟撤N原因，我不能出席這次會(huì)議。
4. I can't say for certain.
   我說(shuō)不準(zhǔn)。
5. I don't know for certain.
   我確實(shí)不知道。
6. I can't say for certain what to do.
   我說(shuō)不準(zhǔn)該做什么。
7. I can't say for certain when he will arrive.
   我說(shuō)不準(zhǔn)他什么時(shí)候會(huì)來(lái)。