The quality or state of being comatose; the condition of unconsciousness or deep unresponsiveness.
From comatose + -ness (suffix forming abstract nouns describing states or qualities). Follows standard English word formation patterns.
The 'ness' suffix is so productive in English that you can technically add it to almost any adjective—but 'comatoseness' sounds awkward because we usually just say 'coma' or 'unconsciousness' instead of the longer version.
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