The act of marking something off a list as complete or verified; or a box or space next to an item that you mark to show it's done.
From 'check' (to verify) and 'off' (indicating completion). This compound emerged in the early 20th century with the popularity of checklists in business and administration.
Psychologically, checking off completed tasks releases dopamine in your brain—which is why apps like Todoist became so addictive; the simple action of 'checkoff' literally rewards your brain.
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