tran·quil 
(trăngkwəl, trăn-)
(trăngkwəl, trăn-)adj.
1. Free from commotion or disturbance: a tranquil lake; a tranquil evening.
2. Free from anxiety, tension, or restlessness; composed: a tranquil mind. See Synonyms at calm.
3. Steady; even: a tranquil flame.
[Middle English tranquill, from Latin tranquillus; see kweiə- in the Appendix of Indo-European roots.]
tranquil·ly adv.
tranquil·ness n.