Word of the day widget
Despite the title, this needs the ability to select additional words. Whereas the one-per-day concept makes sense as an addendum when a word is looked up, in the Today area it needs continual functionality to justify the space, and not stupidly remain as mere clutter for the rest of the day. Also, it acts as a digest or game in this location, furthering the point of increasing vocabulary; restricting that to one word per day is obviously counterproductive.
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Writing Aid — Dictionary & Word of the Day widget