Warm currents of air or water that rise upward, or clothing designed to provide thermal insulation and trap body heat.
From Greek 'therme' meaning 'heat.' The modern meaning developed separately in meteorology (warm air currents) and fashion (insulating clothing).
Birds like eagles use thermals—invisible columns of hot air—to soar for hours without flapping, gaining altitude for free by catching invisible 'elevators' of warm air!
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