An archaic or dialectal word for a single grain or a small step or degree in progression.
From Old English 'gre(o)n' related to 'grain,' used to describe small discrete units or minimal measures, now largely obsolete except in specialized regional dialects.
Medieval English speakers had dozens of ways to say 'tiny'—grein suggests incremental thinking, where progress happened grain by grain, a perfect word for a world measured in handfuls and thimblefuls.
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