Observe v. t. : To take notice of by appropriate conduct; to conform one's action or practice to; to keep; to heed; to obey; to comply with; as, to observe rules or commands; to observe civility.

Observe v. t. : To be on the watch respecting; to pay attention to; to notice with care; to see; to perceive; to discover; as, to observe an eclipse; to observe the color or fashion of a dress; to observe the movements of an army.

Observe v. t. : To express as what has been noticed; to utter as a remark; to say in a casual or incidental way; to remark.

Observe v. i. : To take notice; to give attention to what one sees or hears; to attend.

Observe v. i. : To make a remark; to comment; -- generally with on or upon.

Example:
What should I Observe on a plant in a water quality experiment?

Taxonomy
bias, Naturalistic observation, Confirmation bias, measurement, behavior, researchers, scientific instruments, drawing conclusions, free encyclopedia, recording, science, observers, human senses, interaction, natural phenomenon, hypothesis, the experiment, fields of science.

Defination from the web:
observations made at different times and places by different people. ... "Observe always that everything is the result of a change, and get used to thinking that there is nothing Nature loves so well as to change ...