- capable of being or liable to be observed; noticeable; visible; discernible: an observable change in attitude.
- worthy or important enough to be celebrated, followed, or observed: an observable holiday.
- deserving of attention; noteworthy.
adj.c.1600, from Latin observabilis “remarkable, observable,” from observare (see observe). Related: Observably; observability.
- 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.