onset

1. (medicine) The initial phase of a disease or condition, in which symptoms first become apparent.Examples: "the onset of schizophrenia"; "In mild cases of hypergonadism prior to puberty, the onset of physical and mood changes may not be abnormally early or significant enough to cause any psychological or long-term physical complications."; "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."

2. (phonology) The initial portion of a syllable, preceding the syllable nucleus.Examples: "The only regular sources for Sardinian *θ are Lat. ci̯ and ti̯, which are absent from Latin onsets. This means that the substantial number of words starting in *θ, discussed in § 3 – 7, cannot regularly continue a Latin form."

3. (acoustics) The beginning of a musical note or other sound, in which the amplitude rises from zero to an initial peak.

4. (obsolete) Anything added, such as an ornament or as a useful appendage.Examples: "And will with deeds requite thy gentleness: And, for an onset, Titus, to advance Thy name and honourable family, Lavinia will I make my empress."obsolete

5. (archaic) An attack; an assault especially of an army.Examples: "Heralds, from off our towers, we might behold From first to last, the onset and retire Of both your armies"; "Who on that day the word of onset gave."; "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."Synonyms: stormingarchaic