Definition of "when"

What words are used as interrogative pronouns? — Give examples.When are the words, what, which, and that, called adj. pron.?When are they called interrogative pronominal adjectives?

1834, Samuel Kirkham, English Grammar in Familiar Lectures, page 117

The Celebrity, by arts unknown, induced Mrs. Judge Short and two other ladies to call at Mohair on a certain afternoon when Mr. Cooke was trying a trotter on the track. […] Their example was followed by others at a time when the master of Mohair was superintending in person the docking of some two-year-olds, and equally invisible.

1897 December (indicated as 1898), Winston Churchill, chapter IV, in The Celebrity: An Episode, New York, N.Y.: The Macmillan Company; London: Macmillan & Co., Ltd., pages 58–59

Turning back, then, toward the basement staircase, she began to grope her way through blinding darkness, but had taken only a few uncertain steps when, of a sudden, she stopped short and for a little stood like a stricken thing, quite motionless save that she quaked to her very marrow in the grasp of a great and enervating fear.

1914, Louis Joseph Vance, “Accessary After the Fact”, in Nobody, New York, N.Y.: George H[enry] Doran Company, published 1915, page 48

Energy has seldom been found where we need it when we want it.

2013 July-August, Henry Petroski, “Geothermal Energy”, in American Scientist, volume 101, number 4

The Baggies had offered little threat until the 28th minute, but when their first chance came it was a clear one.

2012 April 22, Sam Sheringham, “Liverpool 0-1 West Brom”, in BBC Sport

I am at London only to provide for Monday, when I shall use that favour which my Lady Bedford hath afforded me, of giving her name to my daughter; which I mention to you, […]

1839, John Donne, The Works of John Donne: Sermons, Letters, Poems, page 310

He sat at the door of his kitchen watching, and seeing there was nothing else for it we buckled to and soon had the job done; when we were admitted to the kitchen and given a really good meal.

1929, Donald John Munro, The Roaring Forties and After, page 38

Oh age! / Where only wealthy men are counted happy: / How ſhall I pleaſe thee? how deſerve thy ſmiles? / When I am only rich in miſery?

c. 1604–1626, doubtfully attributed to Francis Beaumont, John Fletcher, “The Faithful Friends”, in Henry [William] Weber, editor, The Works of Beaumont and Fletcher, in Fourteen Volumes: […], volume I, Edinburgh: […] F[rancis] C[harles] and J[ohn] Rivington; […], published 1812, Act II, scene ii, page 53

[...] ſhortly [...] I'le reſolue you [...] / Theſe happend accidents: till when, be cheerefull [...]

1610–1611 (date written), William Shakespeare, “The Tempest”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act V, scene i], page 18, column 2

Homer, to whom the Muses did carouse / A great deep cup with heav'nly nectar fill'd, / The greatest, deepest cup in Jove's great house, / (For Jove himself had so expressly will'd) / He drank off all, nor let one drop be spill'd; / Since when, his brain that had before been dry, / Became the well-spring of all poetry.

1831 (published), John Davies, Orchestra Or, a Poem of Dancing, in Robert Southey, Select Works of the British Poets: From Chaucer to Jonson, with Biographical Sketches, page 706

For the moment, suffice it to say that the stories told through the whens and hows of building a scene differentiate individual desires and needs more clearly than shared speech was up to then able to communicate.

2008, Paolo Aite, Lanscapes of the Psyche, Ipoc Press, page 151

When we go out to a restuarant, we're the guys who never say "when" when the waiter is grinding fresh pepper on our salads.

2004, Andy Husbands, Joe Yonan, The Fearless Chef: Innovative Recipes from the Edge of American Cuisine, page 83

He keeps the bottle in the top bureau drawer; he takes it out, and two glasses, and pours. Say when. When, please.

2009, Margaret Atwood, The Blind Assassin, page 111

Producers have the power to say "when" when the actress involved is too stressed to continue. That's responsible filmmaking.

2011, Fritz Allhoff, Dave Monroe, Porn - Philosophy for Everyone: How to Think With Kink

Why when I ſay? […] Off with my boots, you rogues: you villaines, when? […] Out you rogue […]

c. 1590–1592 (date written), William Shakespeare, “The Taming of the Shrew”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act IV, scene i], page 221, column 2

Set parſon, ſet, the dice die in my hand: / VVhen parſon, vvhen! vvhat can ye finde no more?

1600, [Michael Drayton, Richard Hathwaye, Anthony Munday, Robert Wilson], The First Part of the True and Honorable Historie, of the Life of Sir John Old-castle, the Good Lord Cobham. […]‎, London: […] [V[alentine] S[immes]] for Thomas Pauier, […]

VVhy vvhen? begin Sir: I muſt ſtay your leiſure.

c. 1615 (date written), Tho[mas] Middleton, “More Dissemblers besides Women. A Comedy”, in Two New Playes. […], London: […] Humphrey Moseley, […], published 1657, Act V, scene i, page 66