The quality or state of being somewhat dark or having a darkness that is moderate rather than complete.
From 'darkish' (dark + -ish, meaning somewhat dark) combined with the suffix '-ness' (which turns adjectives into nouns describing qualities). This is a double suffix construction that emerged in English to express degrees of darkness.
English speakers use '-ish' to express uncertainty and gradations—'darkish' is actually how we talk in real life! We say 'around 5-ish' and 'bluish' constantly, but adding '-ness' to make abstract nouns of these already-softened adjectives shows how flexible our word-building system is.
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