In a diagram, I added small visual elements to identify specific objects. Should I call these things (visual) marks or (visual) markers? What is the difference? Is there a better term?
According to dictionary.com a mark is a a visible impression or trace on something and a marker is something used as a mark or indication. However, this does not answer my question because the definition of marker is somehow self-referencing: is something used as a mark a mark or a marker?