In physics, particularly in quantum physics, a system observable is a measurable operator, or gauge, where the property of the system state can be determined by some sequence of physical operations. For example, these operations might involve submitting the system to various electromagnetic fields and eventually reading a value off some gauge. In ... Found on http://en.wikipedia.org/wiki/Observable
(from the article `quantum mechanics`) ...equations form an important part of quantum mechanics, it is possible to present the subject in a more general way. Dirac gave an elegant ... Found on http://www.britannica.com/eb/a-z/o/3
Ob·serv'a·ble adjective [ Latin observabilis : confer French observable .] Worthy or capable of being observed; discernible; noticeable; remarkable. Sir. T. Browne. « The difference is sufficiently observable .» Southey. -- Ob*serv'a*ble*ness... Found on http://www.encyclo.co.uk/webster/O/5