alertness vs vigilance

alertness and vigilance both are nouns.

Word	Noun	Adjective	Verb	Adverb
alertness	Yes	No	No	No
vigilance	Yes	No	No	No

As nouns, alertness and vigilance are synonyms defined as:

alertness and vigilance: the process of paying close and continuous attention

Other synonyms of alertness include wakefulness, watchfulness.

alertness (noun)	vigilance (noun)
lively attentiveness	vigilant attentiveness
the process of paying close and continuous attention	the process of paying close and continuous attention
a state of readiness to respond