for certain [fɔ: ˈsə:tn]

以下由轻松背单词网站提供

肯定地；确凿地

I can tell you for certain that I am always honest.我可以肯定地告诉你，我一向是老实的。
But it could be many years before he knows for certain.不过是不是真那么好，还得过许多年后才能确定。