What does unascertainable mean?
Unascertainable means impossible to determine or establish with certainty. It is typically used for facts, causes, identities, quantities, or circumstances that cannot be conclusively established, even after careful investigation. For example, an investigator may report that the cause of a fire was unascertainable because the surviving evidence does not support a definite conclusion. The word is more precise than uncertain, which can describe a belief or conclusion that lacks confidence without necessarily suggesting that certainty is impossible. Unascertainable is also more specific than unknown: something can be unknown because no one has investigated it yet, whereas something unascertainable cannot presently be established by the available means. The term is most common in formal legal, scientific, historical, and investigative contexts. Its usefulness lies in distinguishing genuine limits of knowledge from an ordinary gap in information.
adjectiveUnable to be determined or established with certainty. It refers especially to facts, causes, quantities, or circumstances that investigation cannot conclusively establish.
- Impossible to determine or establish with certainty.
"The exact cause of the disappearance remains unascertainable despite extensive investigations."
"The specimen's age proved unascertainable from its physical characteristics."
"Investigators said that the precise cause of the fire was unascertainable."
When the evidence cannot settle a mystery, the mystery is not merely unsolved—it may be unascertainable.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does unascertainable come from?
The adjective was formed in English by attaching the negative prefix un- to ascertainable. The core word ascertain entered Middle English from Old French and ultimately derives from Latin ad certum, literally 'to the certain,' expressing the idea of finding out with certainty. The English prefix reverses that affirmative meaning to indicate that certainty cannot be reached.
How unascertainable is actually used
This is a formal word common in legal, scientific, historical, and investigative writing. It is stronger than simply saying that something is unknown: it indicates that available evidence or methods cannot conclusively establish the answer.
Easily confused with unascertainable
Unascertainable describes something that cannot be established with certainty, whereas unascertained describes something that has not yet been established.
Uncertain can describe a fact, belief, or decision that is not firmly known, while unascertainable more specifically describes information or circumstances that cannot be determined conclusively.