Hi there, Okay. You want to know the difference. Let me tell you what is perception. Perception is what you perceive through your sensory modalities. Primarily, we have 5 types of perception (sensations): hearing, seeing, smelling,tasting and sensing by your skin like pain etc. Other question is related to the delusion. You know about thought and thought processes. Adults can think rationally and logically.These thoughts are reality based. You say “ Mr so and so is against you” and in reality that person doesn’t even know you. And your friends and family members will all say that what you say is absolutely wrong. So that thought maybe called a delusion. There are other factors involved in to say it a delusion, those are for the mental health professional to decide.