The Collaborative International Dictionary
Certainness
Certainness \Cer"tain*ness\, n. Certainty.
Wiktionary
certainness
n. The state or quality of being certain.
Usage examples of "certainness".
Hear, now, this counsel for your certainness: Upon your most glad day, bear then in mind The unknown harm and woe that come behind.
But now I know, in utter certainness, That in great lordship, if I well advise, There is great servitude in sundry wise.