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.

Source: Webster's Revised Unabridged Dictionary (1913)