(physics, quantum mechanics) The principle that there is an absolute limit on the combined accuracy of certain pairs of simultaneous, related measurements, especially that of the position and momentum of a particle. Originally posited as a problem of measurement, it was soon refined as an inherent property of the universe.

(chemistry) A principle stating that, if a chemical system at equilibrium experiences a change in concentration, temperature, or total pressure, the equilibrium will shift in order to minimize that change.

(physics) The observation that the sums and differences of the frequencies of spectral lines often equal other observed frequencies; a consequence of quantum mechanics.

The axiom that "machines should work; people should think".

(physics) A principle in quantum mechanics that states that no two identical fermions may occupy the same quantum state simultaneously.

(programming, object-oriented programming) principle that states that once an interface has become too large, it needs to be split into smaller and more specific interfaces so that any client of the interface will only know about the methods that pertain to itself. (In other words: no client should be forced to depend on methods it does not use.)

(object-oriented programming) A principle stating that any type having a subtype should be replaceable by its subtype without altering any of the desirable properties (such as correctness, task performed, etc.) of the program.

(object-oriented programming) Design principle that states that (1) High- and low-level modules should both depend on abstractions and (2) instead of abstractions depending upon details, details should depend upon abstractions.

(programming, object-oriented programming) A principle that states that software entities (such as classes, modules, and functions) should be open for extension, but closed for modification.

(software, design) a technique by which classes may achieve polymorphic behavior and code reuse by containing other classes that implement the desired functionality instead using inheritance.