serenity

from The American Heritage® Dictionary of the English Language, 4th Edition

• n. The state or quality of being serene.

from Wiktionary, Creative Commons Attribution/Share-Alike License

• n. The state of being serene; calmness; peacefulness.
• n. A lack of agitation or disturbance.
• n. A title given to a reigning prince or similar dignitary.

from the GNU version of the Collaborative International Dictionary of English

• n. The quality or state of being serene; clearness and calmness; quietness; stillness; peace.
• n. Calmness of mind; eveness of temper; undisturbed state; coolness; composure.

from The Century Dictionary and Cyclopedia

• n. The quality or condition of being serene; clearness; calmness; quietness; stillness; peace: as, the serenity of the air or sky.
• n. Calmness of mind; tranquillity of temper; placidity.
• n. A title of dignity or courtesy given to certain princes and high dignitaries. It is an approximate translation of the German Durchlaucht, more commonly rendered Serene Highness. See serene, 3.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• n. the absence of mental stress or anxiety
• n. a disposition free from stress or emotion