v.
    - look at attentively. 
▸keep under careful or protective observation.
 ▸
(watch for)
 look out for.
 - exercise care, caution, or restraint about. 
▸
[usu. in imper.]
 
(watch out)
 be careful.
 - maintain an interest in.
 - archaic remain awake for the purpose of religious observance.
 
n.
    - a small timepiece worn typically on a strap on one's wrist.
 - an act or instance of watching. 
▸a period of vigil, typically during the night.
 - a fixed period of duty on a ship, usually lasting four hours. 
▸
(also starboard or port watch)
 the officers and crew on duty during one such period.
 ▸a shift worked by firefighters or police officers.
 - 
(also night watch)
 historical a watchman or group of watchmen who patrolled and guarded the streets of a town at night.
 
 
  Phrase
  
    - be on the watch
 be on the alert for danger or trouble.  - keep watch
 stay on the lookout for danger or trouble.  - watch one's 
(or someone's)
 back
 protect oneself (or someone else) against danger from an unexpected quarter.  - the watches of the night
 literary waking hours during the night. 
   
  Derivative
  
  Etymology
  OE wæcce ‘watchfulness’, wæccende ‘remaining awake’; rel. to wake1.