"tranquility" in the noun sense
1. repose, quiet, placidity, serenity, tranquillity, tranquility
a disposition free from stress or emotion
2. tranquillity, tranquility, quiet
an untroubled state free from disturbances
3. tranquillity, tranquility, quietness, quietude
a state of peace and quiet
Source: WordNet® (An amazing lexical database of English)
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