Observation

Observation is either an activity of a living being (such as a human), which senses and assimilates the knowledge of a phenomenon, or the recording of data using instruments. The term may also refer to any datum collected during this activity. Observations are statements which are determined by using the senses. Observations aroused by self-defining instruments are often unreliable­¹. Such observations are hard to reproduce because they may vary even with respect to the same stimuli. Therefore... full article at wikipedia