vigilance

noun

ability to maintain concentrated attention over prolonged periods of time, which could be improved through training and practices

Pronunciation: /ˈvɪd͡ʒɪlɪns/ / /ˈvɪd͡ʒɪləns/

Etymology: Borrowed from Middle French vigilance, from Latin vigilantia.

Alert watchfulness.
“To-night she took her accustomed place; for, during the night, no vigilance could satisfy her but her own: any eye but hers might close in momentary forgetfulness.”
“I corralled the judge, and we started off across the fields, in no very mild state of fear of that gentleman's wife, whose vigilance was seldom relaxed. And thus we came by a circuitous route to Mohair, the judge occupied by his own guilty thoughts, and I by others not less disturbing.”
Close and continuous attention.
“But you must remember, my fellow-citizens, that eternal vigilance by the people is the price of liberty, and that you must pay the price if you wish to secure the blessing.”
A guard; a person set to watch.