Observer
Part of speech: noun
Definition: One who makes observations, monitors or takes notice One who adheres or follows laws, guidelines, etc. A person sent as a representative, to a meeting or other function to monitor but not to participate A crew member on an aircraft who makes observations of enemy positions or aircraft A sentry etc. manning an observation post
Example sentence: People who look for the first time through a microscope say, 'Now I see this, and then I see that,' and even a skilled observer can be fooled. On these observations I have spent more time than many will believe, but I have done them with joy, and I have taken no notice of those who have said, 'Why take so much trouble,' and, 'What good is it?'
Percipient
Part of speech: adjective
Definition: Having the ability to perceive, especially to perceive quickly.Perceiving events only in the moment, without reflection, as a very young child.
Part of speech: noun
Definition: One who perceives something.One who has perceived a paranormal event.