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.
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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.
Traces left behind by organisms may not survive over time, observable signals may be too faint to identify, or existing technologies may simply be unable to detect them.
From Science Daily • Jun. 30, 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
When participation requires visible sacrifice—time, money, behavioral constraint—commitment becomes observable.
From The Wall Street Journal • Apr. 19, 2026
One of these regions would become what we now see as the observable universe.
From "A Brief History of Time: And Other Essays" by Stephen Hawking
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.
