vigi-, vig-

Be vigilant.

1. To keep watch, to supervise, to monitor: "Grandmother sat on the front steps and invigilated her grandchildren as they played in the yard."
2. Primarily British, to keep watch over students at an examination to prevent cheating.
3. Etymology: a descendant of the Latin verb vigilare, meaning "to stay awake".

The Latin vigilare is the ancestor of English vigilant, "watchful", and it also gives English reveille, "a signal to wake up in the morning"; via French réveiller; as well as, surveillance, "close watch, supervision", from French surveiller.

Signal on a drum or a bugle at sunrise. Etymology: From French reveillez, "wake up"; from Middle French reveiller, "to awake, to rouse", from re- and eveiller, from Old French esveillier, from Vulgar Latin exvigilare, from ex-, "upward" and Latin vigilare, "to watch".

1. Continual observation of a person or a group; especially, one suspected of doing something illegal.
2. Close observation of a person or a group; especially, one under suspicion.
3. The act of observing or the condition of being observed.
4. Etymology: from French surveillance, "oversight, supervision, a watch"; a noun of action from surveiller, "oversee, watch"; from sur-, "over" + veiller, "to watch" from Latin vigilare, from vigil, "watchful, awake, wakeful".

1. Watchful and alert, especially to guard against danger, difficulties, or errors.
2. Carefully observant or attentive; on the lookout for possible danger.
3. Being on the alert; being watchful.