1. Possible to observe: observable phenomena; an observable change in demeanor.
2. Archaic Deserving or worthy of note; noteworthy: an observable anniversary.
A physical property, such as weight or temperature, that can be observed or measured directly, as distinguished from a quantity, such as work or entropy, that must be derived from observed quantities.
The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2019 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.