onset

Etymology

From on- + set. Compare Old English onsettan (“to impose; oppress, bear down”).

noun

1. (archaic) An attack; an assault especially of an army.
   Who on that day the word of onset gave. 1800, William Wordsworth, Six thousand Veterans
   And Peter's tired army cheered, and the newcomers roared, and the enemy squealed and gibbered till the wood re-echoed with the din of that onset. 1950, C. S. Lewis, The Lion, the Witch and the Wardrobe
2. (medicine) The initial phase of a disease or condition, in which symptoms first become apparent.
   the onset of schizophrenia
   Widely credited as an early pioneer of the modern railway, Shooter died peacefully of his own choosing in Switzerland on December 13, having bravely lived with the onset of motor neurone disease in the final years of his life. December 28 2022, Paul Stephen, “Network News: Adrian Shooter CBE: rail industry mourns "a great man"”, in RAIL, number 973, page 6
3. (phonology) The initial portion of a syllable, preceding the syllable nucleus.
   Holonym: syllable
4. (acoustics) The beginning of a musical note or other sound, in which the amplitude rises from zero to an initial peak.
5. A setting about; a beginning.
   the onset of puberty
   Floods in northern India, mostly in the small state of Uttarakhand, have wrought disaster on an enormous scale. The early, intense onset of the monsoon on June 14th swelled rivers, washing away roads, bridges, hotels and even whole villages. Rock-filled torrents smashed vehicles and homes, burying victims under rubble and sludge. 2013-06-29, “High and wet”, in The Economist, volume 407, number 8842, page 28
6. (obsolete) Anything added, such as an ornament or as a useful appendage.

verb

1. (obsolete) To assault; to set upon.
2. (obsolete) To set about; to begin.