The Core of the Corps Is Loyalty
But if you use the wrong form of the word pronounced /kohr/, you will have little loyalty from your editors or your employers.
Core means the middle, the base, the main parts. An apple core, core curriculum, core values … all basics.
Corps means a body of people acting as a single group. The Marine Corps, the Press Corps, the Corps of Engineers … all teams united by a common purpose.
The best way to remember the difference is that if you are talking about a body, it’s a corps — think of a corpse without the E … they come from the same root word. Pretty much anything else is a core.