ascertain

Etymology

From Middle English acerteynen, from Old French acertener, from a- (“to, towards”) + certener (“make sure of”), from the adjective certain, from Latin certus (“certain, fixed”). Compare to Spanish acertar.

verb

1. To find out definitely; to discover or establish.
   As soon as we ascertain what the situation is, we can plan how to proceed.
   Walk the dog in the pounding rain / Looking for a way out of my brain, trapped in it / But I cannot ascertain that I'm trapped in it / Or that the traps even real so I remain trapped in this chambers 2023, “Split The Atom”, in Kae Tempest (lyrics), Nice Idea
2. (obsolete) To make (someone) certain or confident about something; to inform.
   Therfore the saide cõmissioners shall mowe say that nowe late during the parlement the King ascertaigned of the saide maliciouse pʳpose of his enemys, willed and desired the lords being then present to shewe their̃ good willes aide and helpe for the saide rescues[…] 1436, Sir Nicholas Harris Nicolas, editor, Proceedings and Ordinances of the Privy Council of England, volume IV, published 1835, page 352c
   We would most gladly ye came yourself if that ye may […] praying you to ascertain us of your News. 1844 [1483], Caroline A. Halsted, quoting Richard III, chapter XV, in Richard III as Duke of Gloucester and King of England, page 307
   Muncer Assured them, that the design was approved of by Heaven, and that the Almighty had in a dream ascertained him of its success. 1769, William Robertson, “The History of the Reign of the Emperor Charles V”, in George Gleig, editor, The Historical Works of William Robertson, volume V, Edinburgh: Doig & Stirling, published 1813, page 395
3. (archaic) To establish, to prove.
   The two firſt lines of the following book ſeem to aſcertain the true meaning of the concluſion of this, and to prove ſufficiently that by Ωκεανός here, Homer could not poſſibly intend any other than a river. 1791, William Cowper, Homer’s Odyssey, volume II, book XI, page 274 (footnote)
   In 1695 he Walter Moyle] was chosen to represent the borough of Saltash in parliament ; a circumstance which ascertains the piece before us to have been written subsequent to that period. 1800, Edward Malone, The Critical and Miscellaneous Prose Works of John Dryden, volume III, London: H. Baldwin and Son, page 382 (note 8)
   We must look somewhat deeper would we learn why a book which now tries our patience was not undeserving of those multiplied editions which have ascertained its popularity. 1842, Isaac D'Israeli, “The Ship of Fools”, in Amenities of Literature: Consisting of Sketches and Characters of English Literature, volume I, Paris: Baudry, page 254
4. (archaic) To ensure or effect.
   It is true, that no diligence can aſcertain ſucceſs ; death may intercept the ſwifteſt career ; but he who is cut off in the execution of an honeſt undertaking, has at leaſt the honour of falling in his rank, and has fought the battle, though he miſſed the victory. 1751-06-29, Samuel Johnson, The Rambler, volume III, number 134, London: A. Millar et al., published 1761, page 155
   The ministry, in order to ascertain a majority in the house of lords, persuaded the queen to take a measure which nothing but necessity could justify. 1757–65, Tobias Smollet, chapter X, in The History of England from the Revolution to the Death of George II, volume II, London: Richardson & Co., published 1830, page 224
   On the contrary, the Squire’s influence as a man of family and property, in the immediate neighbourhood, who actually kept greyhounds, and at least talked of hunters and races, ascertained him the support of the whole class of bucks, half and whole bred, from the three next counties ; and if more inducements were wanting, he could grant his favourites the privilege of shooting over his moors, which is enough to turn the head of a young Scotchman at any time. 1824, Sir Walter Scott, “Administration”, in St. Ronan's Well, Boston: Samuel H. Parker, page 29