system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:Can someone explain what an isomer is in layman's terms?
gpt
An Isomer is a molecule with the same kind of atoms, but they are are a different shape.  
Imagine a lego set, put it together one way to make a plane.  
Take the plane apart, use all of those pieces to make a ship.  
The ship and the plane are isomers of each other, same stuff, different arrangement.
   
EDIT: OK just might want to make this clear, the ship doesn't actually have to be made out of the plane, they just use the same kind of pieces in the same amounts.