Synonyms

ascertain

American

[as-er-teyn] / ˌæs ərˈteɪn /

verb (used with object)

to find out definitely; learn with certainty or assurance; determine.

to ascertain the facts.
Archaic. to make certain, clear, or definitely known.

ascertain British

/ ˌæsəˈteɪn /

verb

to determine or discover definitely
archaic to make certain

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

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

Inflected Forms

Participles

Conjugated Forms

Present

Past

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.

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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.

See Examples For:

ascertain ascertains ascertained ascertaining

“He was nearby on the scene there, and we were working trying to ascertain his identity and the motivations behind that,” Hicks said.

From The Wall Street Journal ● Aug. 2, 2026

Without further information, it is impossible to ascertain their validity.

From BBC ● Jul. 17, 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

“My job was to ascertain if the casualty warranted the risk,” said Kelley.

From "Boots on the Ground: America's War in Vietnam" by Elizabeth Partridge

Henry plays it safe: He ascertains John is gay so shares his chapters via mail.

From Washington Post ● Dec. 29, 2022

On the other hand, logical analysis ascertains whether the premises of an argument support the conclusion.

From Textbooks ● Jun. 15, 2022

“Insikt Group ascertains with high confidence that the top tools on underground forums will continue to change,” the report said.

From Fox News ● Jul. 27, 2019

“The court looks at the impact and the motivation - if it is an ethical violation, if it is an administrative violation - and then ascertains if the punishment fits the crime,” Grevemberg said.

From Washington Times ● Apr. 2, 2018

According to the narrative of Herodotus, Cyrus does not simply command the Persians to take up arms against the Medes, but he assembles the tribes, and ascertains their feeling.

From The History of Antiquity Vol. V. by Max Duncker

The researchers also assessed severity of CTE and found a connection between high grade CTE and dementia before death, with the latter ascertained by the players' medical notes and interviews with family members.

From Barron's ● Aug. 25, 2026

A third person whose injuries had yet to be ascertained was in the process of being brought to hospital.

From Barron's ● Aug. 21, 2026

Mr Lawson said the pioneering work had even ascertained where the people, who were buried between the 12th Century and 1560, were born.

From BBC ● Nov. 3, 2025

She’s ascertained that she’s not a child and not an adult; not the sick little girl named Marcy who she used to be, nor her maker’s favorite.

From Salon ● Sep. 24, 2025

A cell’s metabolic identity—i.e., whether it was consuming lactose or glucose—could be ascertained not by the sequence of its genes, which was always constant, but by the amount of RNA that a gene was producing.

From "The Gene" by Siddhartha Mukherjee

The export control amounts to a de facto ban on the model since Anthropic has no way of ascertaining the nationality of its users.

From The Wall Street Journal ● Jun. 16, 2026

Her petition said they are still ascertaining the assets to be identified as separate and community property.

From Los Angeles Times ● Aug. 27, 2024

"Studying isolated enzymes is a powerful tool for ascertaining their activity and drawing conclusions about their functional role inside the plant cell," Hart explained.

From Science Daily ● Apr. 24, 2024

But ascertaining numbers has been stymied by privacy limits that Capasa said the new survey hopes to overcome.

From Seattle Times ● Feb. 21, 2024

In the autumn of 1971 a man used to come to our house, bearing confections in his pocket and hopes of ascertaining the life or death of his family.

From "Interpreter of Maladies" by Jhumpa Lahiri

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023