an act or instance of regarding attentively or watching.
3.
the faculty or habit of observing or noticing.
4.
notice: to escape a person's observation.
5.
an act or instance of viewing or noting a fact or occurrence for some scientific or other special purpose: the observation of blood pressure under stress.
Origin: 1350–1400; Middle English < Latin observātiōn- (stem of observātiō), equivalent to observāt(us) (past participle of observāre to observe) + -iōn--ion