noun

• (uncountable) Doubt; the condition of being uncertain or without conviction.
  "“Well,” I answered, at first with uncertainty, then with inspiration, “he would do splendidly to lead your cotillon, if you think of having one.” ¶ “So you do not dance, Mr. Crocker?” ¶ I was somewhat set back by her perspicuity."
• (countable) Something uncertain or ambiguous.
  "Despite these uncertainties, Clarke told MPs he was convinced of the need to order trains powered by batteries. He said: "We're calling for a 'no regrets' order of battery trains because we see them always having a future. We see them being fundable, financeable, similar cost to diesel trains, and we know that however much electrification we would aspire to do, there's always going to be at least a third of the network that isn't electrified."
• (uncountable, mathematics) A parameter that measures the dispersion of a range of measured values.