ascertain
Americanverb (used with object)
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to find out definitely; learn with certainty or assurance; determine.
to ascertain the facts.
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Archaic. to make certain, clear, or definitely known.
verb
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to determine or discover definitely
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archaic to make certain
Usage
What are other ways to say ascertain?
To ascertain something is to determine it or learn it with certainty or assurance. How is ascertain different from the learn, discover, and detect? Find out on Thesaurus.com.
Other Word Forms
Derived Forms
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preascertainmentnoun
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ascertainablyadverb
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ascertainableadjective
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ascertainmentnoun
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unascertainableadjective
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ascertainernoun
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nonascertainableadjective
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well-ascertainedadjective
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unascertainablyadverb
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unascertainedadjective
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nonascertainablyadverb
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nonascertainablenessnoun
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preascertainverb (used with object)
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nonascertainmentnoun
Conjugated Forms
Present
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has ascertainedperfect 3rd person singular
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have ascertainedperfect
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have been ascertainingperfect progressive
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are ascertainingprogressive
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ascertainssingular 3rd person
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am ascertainingprogressive 1st person singular
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is ascertainingprogressive 3rd person singular
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ascertainingparticiple
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has been ascertainingperfect progressive 3rd person singular
Past
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had ascertainedperfect
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were ascertainingprogressive plural
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was ascertainingprogressive singular
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ascertainedsimple
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had been ascertainingperfect progressive
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ascertainedparticiple
Future
Etymology
Origin of ascertain
First recorded in 1400–50; late Middle English, variant of acertain, assertain, from Middle French acertain-, stem of acertener “to make certain”; equivalent to a- 5 + certain
Explanation
Ascertain is a verb that means to find out something. You might have to go to the bank to ascertain if there is any money in your account. This is a formal word that often applies to discovering the facts or truth about something through examination or experimentation. Information that is ascertained is certain beyond a doubt. If you want a less formal synonym, use discover.
Vocabulary lists containing ascertain
The Vocabulary.com Top 1000
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Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
Technological limitations make it impossible to ascertain precisely where Misiorowski ranks in the pantheon of baseball’s great fastball artists.
From The Wall Street Journal • Jun. 5, 2026
The reason it is hard to ascertain to what extent spying has been a part of Eckert's development is he has conducted no media interviews since the scandal broke.
From BBC • Jun. 3, 2026
We just never noticed because we kept looking down at our feet, trying to ascertain a way out.
From Salon • May 30, 2026
Officials said they are also in communication with authorities to ascertain the cause of death, obtain the complete medical record and review the circumstances surrounding the death.
From Los Angeles Times • Mar. 30, 2026
“The laws of this state permit the hearing of evidence to ascertain the degree of responsibility. And, also, the law permits the offering of evidence toward the mitigation of punishment.”
From "Native Son" by Richard Wright
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
