at a distance from something or somebody else in space or time
They lived in towns 20 miles apart
Her exams were three days apart
at a distance in character or quality
Their ideas are worlds apart
so as to separate one from another
You can't tell the twins apart
excluded from consideration
Joking apart, what shall we do?
in or into two or more parts
They had to take the engine apart
[Middle English, from early French a part to the side]