Synonyms of the word 
CASUALNESS → FAMILIARITY - INFORMALITY
casualness
- n. The state of being casual.
- n. A relaxed and nonchalant attitude.
familiarity
- n. The state of being extremely friendly; intimacy.
- n. Undue intimacy; inappropriate informality, impertinence.
- n. An instance of familiar behaviour.
- n. Close or habitual acquaintance with someone or something; understanding or recognition acquired from experience.
informality
- n. The condition of being informal.
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