Belonging to or characteristic of a principal, dominant, or widely accepted group, movement, or style. The prevailing current of thought, influence, or activity in a particular area.
Originally a 19th-century term for the main current of a river, from 'main' + 'stream.' The metaphorical use meaning 'prevailing trend' emerged in the early 20th century, popularized in political and cultural contexts by the 1950s.
The river metaphor is perfect - just as tributaries flow into the main stream, cultural ideas from margins often flow into mainstream acceptance! What's considered 'mainstream' varies dramatically by geography and generation, making it a constantly shifting target.
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