Keeping careful watch for possible danger or difficulties; being alertly watchful and prepared to respond quickly. It implies sustained attention and readiness to act when necessary.
From Latin 'vigilans', present participle of 'vigilare' meaning 'to stay awake, watch'. The root 'vigil' means 'awake, watchful', related to 'vigere' (to be lively, flourish). The word entered English in the 15th century, originally describing literal wakefulness but expanding to mean alert watchfulness in any context.
Vigilance is evolution's gift to survival - our ancestors who stayed vigilant lived longer and passed on those genes! Interestingly, chronic vigilance (hypervigilance) can become exhausting and counterproductive, which is why healthy vigilance involves knowing when to be alert and when to relax, like a security guard who stays sharp by varying their attention patterns.
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