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.
Astronomers estimate that the observable universe contains roughly 1 trillion galaxies.
From Science Daily • Jun. 24, 2026
In other words, different physical processes can produce very similar observable signatures, making it challenging for the AI to correctly identify which parameter is responsible.
From Science Daily • Jun. 11, 2026
The marriage recession varies in scope and speed but is observable in nearly every country on earth.
From The Wall Street Journal • May 28, 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
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.
