The ending of a romantic relationship; or the breaking apart of something solid.
From 'break' + 'up,' a phrasal verb construction. As one word (noun), it became standard in American English in the 1900s to describe relationship dissolution.
Breakup' is a relatively young word—for centuries people just said 'parted ways' or 'separated,' but modern psychology in the 1900s created the concept of 'break ups' as a discrete emotional event worth naming!
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