You are having no problem differentiating some subtle difference - they are pronounced the same way! It is the context of the conversation and the syntax which tells the listener which word you mean eg
(Talking about somebody having died and...)
He is in mourning versus He is in morning???? - that 'is in morning' doesn't make sense
(Talking about the arrival of somebody...)
He's coming in the morning versus He's coming in the mourning??? - doesn't make sense. But in the context of a death, it would be clear what you were meaning if you said, He's coming in the mourning party.
Student or Learner