ascertain

1 of 2

verb

as·​cer·​tain ˌa-sər-ˈtān 

ascertained; ascertaining; ascertains

transitive verb

1

: to find out or learn with certainty

ascertain the truth

trying to ascertain the cause of the fire

information that can be easily ascertained on the Internet

2

archaic : to make certain, exact, or precise

ascertainable

ˌa-sər-ˈtā-nə-bəl 

adjective

ascertainment

ˌa-sər-ˈtān-mənt 

noun

ascertainment

2 of 2

noun

as·​cer·​tain·​ment ˌa-sər-ˈtān-mənt 

plural -s

: the act of ascertaining:

a

archaic : a reducing to certainty : exact determination

that a period might be put and some ascertainment made and a time fixed

—Oliver Cromwell

b

: a finding out (as by investigation) : discovery

his work … was the ascertainment of historical truth

—Arnold Bennett

Synonyms of ascertain

Verb

• discover
• realize
• see
• hear
• learn
• find

Choose the Right Synonym for ascertain

discover, ascertain, determine, unearth, learn mean to find out what one did not previously know.

discover may apply to something requiring exploration or investigation or to a chance encounter.

discovered the source of the river

ascertain implies effort to find the facts or the truth proceeding from awareness of ignorance or uncertainty.

attempts to ascertain the population of the region

determine emphasizes the intent to establish the facts definitely or precisely.

unable to determine the origin of the word

unearth implies bringing to light something forgotten or hidden.

unearth old records

learn may imply acquiring knowledge with little effort or conscious intention (as by simply being told) or it may imply study and practice.

I learned her name only today

learning Greek

Examples of ascertain in a Sentence

Verb

We look at digital media—images, audio and video—and we try to ascertain whether or not they've been manipulated. We use mathematical and computational techniques to detect alterations in them. —Claudia Dreifus, New York Times, 2 Oct. 2007

Currently, an official trying to ascertain road damage in the aftermath of an earthquake might have to keep one eye on the TV news while listening to both radio traffic reports and the police scanner. Since most of these data are available in digital form, the software could take them all in, process them and present a report outlining the best evacuation routes. —Kevin Hogan, Technology Review, April 2002

With an equation linking the money wage to prices, the degree of inflation could be ascertained. —Sidney Weintraub, Modern Economic Thought, (1977) 1993

Recent Examples on the Web

Verb

Who had what — or more specifically, half of what — must be ascertained before figuring in tax and tip. — Inga, San Diego Union-Tribune, 15 June 2026

One person was killed by a car bomb in Moscow's eastern suburbs early on Tuesday, the Investigative Committee of the Russian Federation announced in a statement, with an investigation now underway to ascertain the details of the incident. — David Brennan, ABC News, 9 June 2026

Screening can begin in primary care with shoes-off exams, when damage from diabetes could be visible; ankle measurements to ascertain swelling, or ultrasounds if warranted. — Elizabeth Cooney, STAT, 8 June 2026

When a woman is discharged after birth, the burden is on her and her family to ascertain potential complications and seek timely care. — Yenupini Joyce Adams, The Conversation, 27 May 2026

Word History

Etymology

Verb

Middle English acertainen to inform, give assurance to, from Anglo-French acerteiner, from a- (from Latin ad-) + certein, certain certain

First Known Use

Verb

15th century, in the meaning defined at sense 2

Rhymes for ascertain

• aeroplane
• appertain
• capitaine
• cassegrain
• cellophane
• chatelaine
• counterpane
• entertain
• halothane
• hurricane
• hyperplane
• inhumane

Kids Definition

ascertain

verb

as·​cer·​tain ˌas-ər-ˈtān 

: to learn with certainty : find out

could not ascertain the correct date

ascertainable

-ˈtā-nə-bəl 

adjective

ascertainment

-ˈtān-mənt 

noun