VIGILANT (VIJ uh lunt) adj constantly alert; watchful; wary
- Miss  Grimble is  vigilant    against grammatical errors; when    she spots   a   misplaced   modifier,
she pounces like a tiger. - Dad   vigilantly  guarded the door    of  the living  room    to  keep    the children    from    seeing  the
Easter Bunny at work. 
To be vigilant is to exhibit vigilance (VIJ uh luns).
- Distracted    by  the loud    noise   in  the hallway,    the guard   let his vigilance   slip    for a   moment,
and the prisoner quickly escaped. 
Vigil   is  a   related word    that    refers  to  a   period  of  staying awake   or  peacefully  protesting, as  if
vigilantly  standing    watch.