ascertain

[as-er-teyn]

verb (used with object)

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

   to ascertain the facts.

2. Archaic.,  to make certain, clear, or definitely known.

ascertain

/ ˌæsəˈteɪn /

verb

1. to determine or discover definitely

2. archaic,  to make certain

Other Word Forms

• ascertainable adjective
• ascertainably adverb
• ascertainer noun
• ascertainment noun
• nonascertainable adjective
• nonascertainableness noun
• nonascertainably adverb
• nonascertainment noun
• preascertain verb (used with object)
• preascertainment noun
• unascertainable adjective
• unascertainably adverb
• unascertained adjective
• well-ascertained adjective

Word History and Origins

Origin of ascertain¹

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

Word History and Origins

Origin of ascertain¹

C15: from Old French acertener to make certain

Example Sentences

The operation also included members of the National Guard, prompting the National Immigration Law Center to file a Freedom of Information Act to ascertain the military’s role in the operation.

From Los Angeles Times

However, precise membership numbers remain difficult to ascertain.

From Salon

Since returning from Asia on Monday, Maddison has undergone tests in recent days to ascertain the severity of the injury.

From BBC

The man gave a false name of John Lesley, but provided his actual date of birth and a mobile phone number, so the force was able to ascertain his real identity as Barclay.

From BBC

When questioned he had initially given a false name of John Lesley, but provided his real telephone number and police were able to ascertain his true identity.

From BBC

Related Words

• confirm 
• determine 
• divine 
• double-check 
• find out 
• verify 

When To Use

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.