I am referring to the NOUN forms of these three words. An excuse, a reason, a cause.
To be absent from school you need an excuse, a reason, or a cause.
There is no excuse for bad behavior, but there is likely a reason for it and a cause.
Drought is the reason for the high water prices. Climate change is the cause of the drought. There is no excuse for unnatural global warming.
Here the use of these synonyms has moved from the general to the specific. Excuse, reason, and cause are interchangeable in general. But their definitions define and delimit their reach.
Excuse defined: an explanation or a reason for an action. An example of an excuse is a student saying that his dog ate his homework.
- An explanation offered to justify or obtain forgiveness.
- A reason or grounds for excusing: Ignorance is no excuse for breaking the law.
- The act of excusing.
- A note explaining an absence.
Reason defined: the cause for something to happen or the power of your brain to think, understand and engage in logical thought.
- An example of reason is when you are late because your car ran out of gas.
- An example of reason is the ability to think logically.
Cause defined: anyone or anything that brings about a result. An example of cause is a washing machine making clothes clean.
- anything producing an effect or result
- a person or thing acting voluntarily or involuntarily as the agent that brings about an effect or result: drinking was the cause of his downfall
- a reason, motive, or ground for some action, feeling, etc.; esp., sufficient reason: cause for complaint
- any objective or movement that a person or group is interested in and supports, esp. one involving social reform
Definitions from Your Dictionary.com