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.

up vote 18 down vote accepted

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. ...

  • 3
    I've deleted my own answer in favour of this, which is more comprehensive. – FumbleFingers Mar 9 '13 at 21:08
  • WOW! This answer solved some of my problems except one! I wanted to ask them one by one myself! :)( – Persian Cat Mar 9 '13 at 21:56
  • I would add (without refs) that X is mandatory means X is a requirement; X is compulsory means something compels one to use/do X. Some mandatory things have few or no teeth behind them to enforce the requirement. Things that are compulsory are typically backed up by some force. The consequences of not respecting compulsory are typically more serious, with more likely and stricter enforcment. A mandatory programming parameter is one that is not optional - the consequences of omitting it are not seismic. A compulsory prison sentence is one that you will not avoid. – Drew Sep 7 '14 at 21:50

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.

  • Compulsory comes from compel - which means to make something happen.
  • Mandatory comes from mandate - which means to say something should happen.
  • Obligatory come from obligation - which is means something is expected.

So compulsory has more of a sense that it will be enforced with some sort of punishment.

  • Etymology can be helpful, but it almost never tells the whole story of meanings, nuances, and implications. (And if you think it is less likely that a king's mandates will be enforced with punishment than his statutes, you've got another think coming.) – Nathan Tuggy May 21 '15 at 1:49
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    I think that with a little more explanation, this might be an interesting way to think about the difference. I do think though that threat of punishment isn't what makes compulsory different from mandatory. I have certain things at my work that are described by our management as mandatory. For example, taking certain training to ensure that I understand our regulatory compliance rules is mandatory. If I don't do the training, I will be punished or fired. – ColleenV May 21 '15 at 2:05
  • Oh I agree that in a lot of cases they are functionally the same, and it's just the feel of them that is different. But i think with edge cases like if something was going to be physically enforced you'd use compulsory, especially if the compulsory thing was something you'd really rather not do. In which case mandatory sounds a bit like doublespeak. For eg if you were writing a dystopian sci-fi novel. – Moolric May 22 '15 at 3:16
  • Or if you were talking about an unwritten rule such as in the expression "compulsory heterosexuality". It's not written anywhere but it is often enforced through social stigma and violence. – Moolric May 22 '15 at 3:23

Basically, mandatory is used in a circular note from school, offices etc. They both are synonyms, but compulsory is usually used in a slightly rude manner when teachers command to do something. Compulsory is to command anyone in a rude manner.

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    I don't see how compulsory can be considered more rude than mandatory. – Gilles Dec 16 '13 at 21:04

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