tran·quil (trăngkwəl, trăn-)
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.]
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2020 by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Indo-European & Semitic Roots Appendices
Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:
The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.