Plural of ballpark; large fields or stadiums where ball games like baseball are played, or general approximate ranges of figures.
From 'ball' plus 'park,' combining game terminology with landscape vocabulary. The phrase 'in the ballpark' (approximately correct) became common in the 1960s as a figurative extension.
The phrase 'in the ballpark' became a mathematical expression because baseball was America's pastime—when people needed to say 'approximately,' they borrowed the idiom from the sport, making math and baseball language permanently connected in American English.
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