Uncertainty, n.; pl. Uncertainties (.
1. The quality or state of being uncertain.
2. That which is uncertain; something unknown. Our shepherd's case is every man's case that quits a moral certainty for an uncertainty. L'Estrange.
Shades of meaning
Fernald has no entry of its own for uncertainty; he lists it under doubt.
Where he writes about it:
As regards practical matters, uncertainty applies to the unknown or undecided; doubt implies some negative evidence. — from doubt
Suspense regards the future, and is eager and anxious; uncertainty may relate to any period, and be quite indifferent. — from doubt