Fatigues are the working uniform soldiers wear day to day. In fatigues, combat fatigues, change out of fatigues.
The name comes from fatigue duty, the manual chores around a base, which is what the clothing was originally for rather than for fighting. The word is plural only, like trousers, so a soldier wears fatigues and never one of them.
1nounfatiguesThe working uniform soldiers wear day to day.
“The soldiers changed out of their fatigues and into their dress uniforms for the parade.”
fatigues is a uniform.