phlogiston

/floʊˈdʒɪstɑn/
noun
  1. A hypothetical substance once believed to be released during burning, now known to be incorrect.
    • Learning about phlogiston helps students see how scientific ideas evolve over time.
    • The phlogiston theory was replaced by the modern understanding of oxygen and combustion.
    • In the 18th century, scientists thought phlogiston escaped from wood as it burned.
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