cheerfulness · noun U /ˈtʃɪr.fəl.nəs/Full view
C2 the state of being happy or bright and pleasant to look at
Dictionary example:

His cheerfulness made us all feel better.

Learner example:

Bright colors are identified with cheerfulness and happiness and dark colors with sadness or feeling down. (Certificate of Proficiency in English; C2; Spanish)

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