The quality or state of being green in color or appearance; greenness.
Formed from 'green' (Old English 'grēne') plus the abstract noun suffix '-th' (similar to 'warmth,' 'width,' 'depth'). This Old English pattern created nouns describing qualities of adjectives.
The '-th' suffix is incredibly old—it goes back to Proto-Germanic and was once the standard way to turn any adjective into an abstract noun, which is why we still have 'truth' and 'strength' but don't say 'greenth' or 'fastth' anymore.
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