Definition of "imperative"

Meantime, alterations at King William Street had become imperative, and by December 22, 1895, the station had been remodelled, as at Stockwell, to provide an island platform with lines each side, and a scissors crossing.

1941 May, “Jubilee of the City Tube”, in Railway Magazine, page 224

Give this document to Ozzy. It's imperative that he reads and understands it. Got it?

2019, Con Man Games, SmashGames, quoting Felix, Kindergarten 2, SmashGames

The suits of kings are imperative.

1612–1626, [Joseph Hall], “(please specify the page)”, in [Contemplations vpon the Principall Passages of the Holy Storie], volumes (please specify |volume=II, V, or VI), London

Anything grandiose or historically based tends to sound flat and banal when it reaches English, partly because translators get stuck between contradictory imperatives: juggling fidelity to the original sense with what is vocally viable, they tend to resort to a genteel fustian which lacks either poetic resonance or demotic realism, adding to a sense of artificiality rather than enhancing credibility.

2014 March 1, Rupert Christiansen, “English translations rarely sing”, in The Daily Telegraph (Review), page R19

The new imperative for investment is the Government's objective to secure carbon-neutral transport emissions by 2040.

2020 December 2, Industry Insider, “The costs of cutting carbon”, in Rail, page 76