to see, watch, perceive, or notice

He observed the passersby in the street.

to regard with attention, esp. so as to see or learn something

I want you to observe her reaction to the judge's question.

to watch, view, or note for a scientific, official, or other special purpose

to observe an eclipse.

to state by way of comment; remark

He observed frequently that clerks were not as courteous as they used to be.

to keep or maintain in one's action, conduct, etc.

You must observe quiet.

to obey, comply with, or conform to

to observe laws.

to show regard for by some appropriate procedure, ceremony, etc.

to observe Palm Sunday.

to perform duly or solemnize (ceremonies, rites, etc.).

to note or inspect closely for an omen or sign of future events.

to notice.

to act as an observer.

to remark or comment (usually fol. by on or upon ).