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
- nonobservable adjective
- nonobservably adverb
- observability noun
- observableness noun
- observably adverb
- unobservable adjective
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.
Though r-star is not directly observable, many of the leading models calculate it to be lower than the current fed-funds rate.
From MarketWatch • Apr. 8, 2026
The JPMorgan analysts said overall 98 percent of the observable oil traffic through the strait was Iranian, averaging 1.3 million barrels a day "in early March".
From Barron's • Mar. 19, 2026
The authors note: “These sites have undergone observable upgrades in recent years, even as Cuba has faced increasingly dire economic prospects that have drawn it closer to China.”
From The Wall Street Journal • Feb. 22, 2026
Coaches call this the “All‑22” view, because all 22 players on the field are simultaneously observable.
From Los Angeles Times • Jan. 22, 2026
Only if the early universe was very smooth and uniform, with a high pressure, can one explain the absence of observable numbers of primordial black holes.
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.
