I am a native English speaker living in Germany. My German colleagues use the term "an operator instruction" to describe a word document with instructions to be carried out by a third party. I have tried to impress upon them that "operator instructions" would be more correct, but I can't explain why! Is this correct and can it be explained via a rule of grammar or style? (The German term "eine Anweisung" is been translated here.) Thank you for your help.