The quality or state of being dozy; sleepiness, drowsiness, or a tendency to doze.
From 'dozy' (sleepy) plus the abstract noun suffix '-ness,' which turns adjectives into nouns representing the quality. Same pattern as 'happy/happiness' or 'sleepy/sleepiness.'
The '-ness' suffix is English's favorite way to make abstract nouns—add it to almost any adjective and you get the feeling! So 'dozy' + 'ness' = the feeling of being sleepy.
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