What is the difference between mandatory and compulsory? Are they synonyms? Can they be used interchangeably especially with regard to something you must do?
Writing the essay is a mandatory task.
Writing the essay is a compulsory task.
English Language Learners Stack Exchange is a question and answer site for speakers of other languages learning English. It only takes a minute to sign up.Sign up to join this community
Compulsory (“Required; obligatory; mandatory”), mandatory (“Obligatory; required or commanded by authority”), and obligatory (“Imposing obligation, morally or legally; binding”) have related and similar meanings.
There are many examples where one of those words could be used in place of another, but in some areas, set phrases arise; for example, compulsory education, compulsory service, mandatory minimum sentences, mandatory retirement, obligatory treatment. For further examples, click the book links at ngrams for compulsory,mandatory,obligatory. Also see ELU question Are the words “mandatory,” “obligatory,” and “compulsory” interchangeable? and similar questions at other sites (1, 2, 3, 4, 5). The differencebetween page is quite informative:
Mandatory and Compulsory are two words that are often confused when it comes to their meanings and connotations. Strictly speaking, there is some difference between the two words. The word ‘mandatory’ is generally used in the sense of ‘binding’. On the other hand, the word ‘compulsory’ is generally used in the sense of ‘essential’. This is the main difference between the two words.
It is important to note that anything that is mandatory has the quality of binding the doer to the work. On the other hand, anything that is compulsory has to be essentially done without postponement. The word ‘compulsory’ often refers to things or requirements. On the other hand, the word ‘mandatory’ often refers to conditions. ...
The authors of the Oxford Learner's Thesaurus argue that "compulsory is used especially in the contexts of education, business, and employment. Mandatory is used especially in the context of the law. Obligatory is often used to talk about rules and laws relating to safety, for example in sport or the workplace."
The authors of the Longman Collocations Dictionary add that mandatory is more formal than compulsory or obligatory and sounds stronger.
Obligatory can also be used humorously. It is almost never used in the attributive position.
So compulsory has more of a sense that it will be enforced with some sort of punishment.