One is vigilant against danger or harm; he may be alert or watchful for good as well as against evil; he is wary in view of suspected stratagem, trickery, or treachery.

J. C. Fernald, English Synonyms and Antonyms (1914)

Example sentences

careful You should be careful in crossing the busy street.
awake Tom lay awake for a long time thinking about Mary.
wary My parents always told me to be wary of strangers.
vigilant One has to be vigilant in these troubled times.
alert When I saw his face, I was instantly on red alert.
expectant In Finland, expectant mothers are given a baby box by the state.

Popularity over time

Word	1850 → 2019	Trend
watchful		rising
careful		steady
awake		rising
wary		rising
vigilant		rising
alert		rising

Use in printed books, per decade from 1850 to 2019.

By length

4 letters: wary²
5 letters: aware², alive², alert², awake², chary²
7 letters: careful², jealous², anxious², guarded², mindful², prudent², wakeful, lidless, heedful
8 letters: cautious², discreet², vigilant³
9 letters: attentive³, sleepless², observant³, expectant³, insomniac⁴, advertent
10 letters: meticulous⁴
11 letters: circumspect³

The small number after each word is its number of syllables (wary² = 2 syllables).