observation

Definitions:

The act of observing or fixing the mind on anything; that which is observed; remark; observance; the angular measurement of any space on the celestial sphere.
- Nuttall's Standard dictionary of the English language. By Nuttall, P.Austin. Published 1914. (noun) (n.) (noun)
The act, power, or habit of taking notice; that which is noticed or learned; fact of being seen; as, he did not escape observation; a remark.
- The Winston Simplified Dictionary. By William Dodge Lewis, Edgar Arthur Singer. Published 1919. (noun) (n.) (noun)
The act of noticing or remarking; the expression in words of what is observed or thought; comment or remark; in Scrip., outward show, as, " the kingdom of God cometh not with observation"; exhibition; in astron. and nav., the angular measurement of any space in the heavens; in science, the act of ascertaining temperature, or of noting or scrutinising some fact or occurrence in nature.
- Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874. (noun) (n.) (noun)
Act of observing: attention: as distinguished from experiment, the act of recognizing and noting phenomena as they occur in nature: that which is observed: a remark: performance.
- The american dictionary of the english language. By Daniel Lyons. Published 1899. (noun) (n.) (noun)
Act of observing; attention; remark.
- The Clarendon dictionary. By William Hand Browne, Samuel Stehman Haldeman. Published 1894. (noun) (n.) (noun)

Usage examples:

But strangest of all was this last observation of hers; that there was nothing of worth in your life that you hadn't to pay a heavy price for.
- The Real Adventure by Henry Kitchell Webster
Still, such a trio moving together through the London streets were hardly likely to escape observation
- A Second Coming by Richard Marsh
Few persons can arrive at anything approaching the real age of the negro, by mere observation unless they are well acquainted with the race.
- Clotelle The Colored Heroine by William Wells Brown