Also referred to as the 'uncertainty' principle, it is a principle in quantum mechanics holding that increasing the accuracy of measurement of one observable quantity increases the uncertainty with which another conjugate quantity may be known.

Behavior is observable.

We are at the centre of the observable universe, keyword being 'observable'.

observable ? i'd say quarks.

Two operators that are also observables, which means that they correspond to some physically measurable quantity. Compatible observables are two or more such operators that can be measured at the same time. Position and momentum are an example of Incompatible observables, since one can only know either the position or the momentum of an object to 100% accuracy.