"The strange new star was at the edge of the observable universe."
2.AdjectiveDeserving to be observed; worth regarding; remarkable.
3.NounAny physical property that can be observed and measured directly and not derived from other properties
"Temperature is an observable but entropy is derived.; In quantum mechanics, observables correspond to Hermitian operators. Also, they act a lot like random variables. Taking their expected value one may recover something resembling a classical observable."