The quality or state of being grubby; the presence of dirt, filth, or uncleanliness.
From 'grubby' (adjective) + -ness (noun suffix creating abstract nouns), a productive pattern in English for naming qualities or states of being.
The -ness suffix is Old English, and it's so ancient that nearly every adjective can take it—'grubbiness' shows how English builds infinite abstract concepts from simple roots!
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