Johnny has a very complete answer but I would disagree that they are synonyms. They are not exactly the same concepts and are not totally interchangeable. As he says at the end of his post, "reason" is a basis for an action or state while "excuse" is a justification for an action or state. For example: "Why were you late for class?" Reason: I missed the bus. Excuse: I stayed up late to study and overslept. This made me miss the bus.

reason is given when u r questioned with the intention of getting from you the correct answer or conducive answer excuse is used when u want to make a real or unreal way of escapism for any work or exercise given to u

"Reason" and "Excuse" are synonyms. Excuse commonly has negative connotations, but not always. Consider the following examples. "What is the reason for your tardiness?" "Do you have an excuse as to why you are late?" "Will you please excuse me?", "May I be excused?" (To be allowed to leave the meeting, perhaps) "I am tired of listening to your excuses!" "It stands to reason that she is wealthy." Reason can not only mean "A basis or motive from action", but also "An underlying fact or cause that provides logic". Excuse can mean "To apoligize", "To grant permission" or "To serve as justification". The two words may be confusing because the noun, excuse, can be defined as "a reason or grounds for excusing". When you use "Reason", try to think about logic, a basis for action. When you use "Excuse", try to think about an explanation to justify action.