observable
American-
A measurable property of a physical system, such as mass or momentum. In quantum mechanics, observables correspond to mathematical operators used in the calculation of measurable quantities. Operators that do not commute, having a nonzero commutator, correspond to observables that cannot be precisely measured at the same time, such as momentum and position.
-
See also uncertainty principle
Other Word Forms
Etymology
Origin of observable
1600–10; < Latin observābilis remarkable, equivalent to observā ( re ) to observe + -bilis -ble
Explanation
Something observable can be perceived or detected — you can see it, hear it, or otherwise sense that it's there. An observable change in the temperature outdoors will make you run back in for your hat and gloves. If an observable hush falls over the dining room when your grandfather clears his throat, it's something that everyone notices. Observable differences between you and your twin sister might include different haircuts and the fact that you wear glasses but she doesn't. Observable things can be sensed (perceived with one of your five senses) or intuited.
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
A few began treating him with observable disdain, including the English teacher who had us read “The Scarlet Letter.”
From The Wall Street Journal • Jun. 10, 2026
The value of these investments is held at cost basis, a securities filing said, unless an observable event such as a new financing round results in a price change.
From MarketWatch • May 22, 2026
A level two volcano is one where there is clearly observable increased volcanic activity and there is the threat of an eruption, and the public is prohibited from certain areas.
From BBC • May 11, 2026
This leads to a spread, or continuum, of observable states rather than a single one.
From Science Daily • Apr. 22, 2026
By comparison, the total number of atoms in your body is about 1028, and the total number of elementary particles—protons and neutrons and electrons—in the observable universe is about 1080.
From "Cosmos" by Carl Sagan
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
