Incident: Needs to be resolved because it is disrupting the process

Problem: Needs a bigger solution, needs to be looked at different angles

Event: Nothing to worry about, can happen

Issue: Like a problem, this needs a bigger solution but also causes a problem

Case: Can be prioritized and planned

So make sure you are talking about the same explanation of what you call something. If you mix-up an event with an incident the result can be disastrous.