What does unpredictable mean?
Unpredictable is an adjective describing something whose occurrence, development, or behavior cannot be forecast with confidence. It may refer to external conditions, such as unpredictable weather or an unpredictable market, or to people and systems whose responses are inconsistent or difficult to anticipate. The word commonly carries a practical implication: plans based on a predictable pattern may fail, so people must remain adaptable. For example, an unpredictable result is one that could not have been anticipated with confidence, while unpredictable behavior suggests that someone does not act consistently enough for others to anticipate their responses. Although unpredictable can sometimes suggest randomness or unpredictability in a broad sense, it usually does not claim that events have no pattern at all. Rather, it emphasizes the limits of certainty and the difficulty of making reliable predictions.
adjectiveNot able to be predicted or forecast with certainty; changing or behaving in an unpredictable way.
- Impossible to predict or forecast with certainty.
- Not consistent, dependable, or easy to anticipate in behavior or character.
"The team's success was unpredictable until the final minutes of the season."
"The storm made the journey across the island unpredictable."
"Her mood was unpredictable, so no one could be certain how she would respond."
Add “un-” to predictable and certainty becomes a warning label.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does unpredictable come from?
Unpredictable was formed in English by adding the negative prefix “un-” to “predictable,” reversing the idea of being able to forecast something. Its roots ultimately trace to Latin praedicere, meaning “to foretell” or “to say in advance,” built from prae-, meaning “before,” and dicere, meaning “to say.” Related English words include predict, prediction, and predictive; preach also reflects the same broader Latin root through a related Latin form.
Related word forms
How unpredictable is actually used
The word is common in both formal and informal English. It can describe events, conditions, systems, and people, and often suggests that a pattern or reliable method of forecasting is absent. It does not necessarily mean that something is completely random.
Easily confused with unpredictable
Unprecedented means never having happened before, whereas unpredictable means that future events or behavior cannot be reliably forecast.