attention!
A command used in schools, military, or sports to order people to stand at attention. Often shouted.
When the teacher said 'Attention!', the students straightened their backs.
standing at attention
The posture or state of standing straight with heels together and arms at the sides. Used as a noun.
We listened to the principal's speech standing at attention.
Standard kanji spelling for the command and the noun.
Variant kanji spelling using 付け instead of つけ.
From 気 (spirit, attention) + を (object marker) + つけ (imperative form of 付ける, to attach). Literally 'attach your attention/spirit', a set phrase for the command 'attention!'.