Plural of drier; machines or devices that remove moisture from something, or places where things dry.
From 'drier' (agent noun from 'dry' via Old English 'dryge'), the plural adds the standard '-s' suffix. The comparative form 'drier' became reanalyzed as a noun referring to the apparatus itself.
The word 'drier' cleverly does triple duty—it's an adjective (more dry), a noun (a machine), and a person (one who dries)—English's word-class flexibility means one spelling covers multiple meanings.
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