The onset of winter brought sudden frosts that threatened the early harvest in the valley.
冬季的来临带来了突如其来的霜冻，威胁到山谷中早熟的收成。
A sleep researcher hypothesizes that exposure to blue light from screens in the hour before bed delays the onset of sleep more than exposure to warm, dim light does.
From a Command of Evidence: Textual question · Information and Ideas
A sleep researcher hypothesizes that dimming household lights in the two hours before bedtime improves sleep onset time more than simply reducing screen brightness alone does.
From a Command of Evidence: Textual question · Information and Ideas
Which choice best defines “onset”?
B — Beginning, start. “onset” means beginning, start.
Which word means “beginning, start”?
D — onset. “onset” means beginning, start.
onset — beginning, start. In Chinese: 开始，发作.
onset is pronounced /ˈɑːnset/.
The onset of winter brought sudden frosts that threatened the early harvest in the valley. (冬季的来临带来了突如其来的霜冻，威胁到山谷中早熟的收成。)
commencement, outset, inception — all close in meaning to onset (beginning, start).
conclusion, end — each the opposite of onset (beginning, start).
Yes. onset is on the SAT Prep Basic list — the everyday academic words the SAT assumes you already have. The Digital SAT does not test vocabulary in isolation; words like this one are tested through Words in Context questions, where you choose the word that completes a passage most logically and precisely.
on(above)+set(setup)