of a certainty 的确
必然
毫无疑问
Certainty \Cer"tain*ty\, n.; pl. {Certainties}. [OF.
certainet['e].]
1. The quality, state, or condition, of being certain.
The certainty of punishment is the truest security
against crimes. --Fisher Ames.
2. A fact or truth unquestionable established.
Certainties are uninteresting and sating. --Landor.
3. (Law) Clearness; freedom from ambiguity; lucidity.
{Of a certainty}, certainly.