The present participle of rain; precipitation falling from clouds in the form of water droplets.
From Old English regn, related to Old Norse regn and German Regen, all from Proto-Germanic *regna-. The verb form developed in Middle English from the noun, following the common pattern of weather phenomena becoming verbs.
The phrase 'it's raining cats and dogs' has puzzled etymologists for centuries, with theories ranging from Norse mythology to the practical observation that heavy rain would wash dead animals through city streets. Interestingly, many languages have similarly bizarre expressions for heavy rain, suggesting humans universally seek colorful metaphors for this common weather event.
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