onset
noun uk/ˈɒn.set/ us/ˈɑːn.set/
the onset of something （指不愉快的事情）的开始，发作
the moment at which something unpleasant begins
the onset of winter 冬季的开始
The new treatment can delay the onset of the disease by several years. 新的治疗方法可以把疾病开始的时间延后几年。
phonetics specialized音节首
the first part of a syllable
Compare: coda rhyme noun