from The American Heritage® Dictionary of the English Language, 4th Edition
- transitive v. To discover with certainty, as through examination or experimentation. See Synonyms at discover.
- transitive v. Archaic To make certain, definite, and precise.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- v. To find out definitely; to discover or establish.
from the GNU version of the Collaborative International Dictionary of English
- transitive v. To render (a person) certain; to cause to feel certain; to make confident; to assure; to apprise.
- transitive v. To make (a thing) certain to the mind; to free from obscurity, doubt, or change; to make sure of; to fix; to determine.
- transitive v. To find out or learn for a certainty, by trial, examination, or experiment; to get to know.
from The Century Dictionary and Cyclopedia
- To make certain; determine; define or reduce to precision by removing doubt, obscurity, or ambiguity; establish; prove.
- To find out by trial, examination, or experiment, so as to know as certain; acquire an accurate knowledge of: as, to ascertain the weight of a commodity or the purity of a metal.
- To make sure of; insure.
- To make certain or sure; certify; assure; inform.
- To establish with certainty; render invariable, or not subject to caprice; fix.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- v. find out, learn, or determine with certainty, usually by making an inquiry or other effort
- v. establish after a calculation, investigation, experiment, survey, or study
- v. be careful or certain to do something; make certain of something
- v. learn or discover with certainty
Middle English acertainen, to inform, from Old French acertener, ascertain- : a-, to (from Latin ad-; see ad-) + certain, certain; see certain.(American Heritage® Dictionary of the English Language, Fourth Edition)
From Old French acertener, from (a- ("to, towards") + certener ("make sure of"), from the adjective certain. (Wiktionary)