Are the words "mandatory," "obligatory," and "compulsory" interchangeable?
As a non-native speaker, I wonder what the rules are for preferring one of "mandatory", "obligatory" or "compulsory" over the others.
The Corpus of Contemporary American English yields examples such as these:
Mandatory: 4865 cases
- mandatory safety nets around trampolines
- mandatory health care reform
- mandatory sentence for first-degree murder
- Unemployment sent me a letter, said this was a mandatory class.
- To stave off matting, daily brushing with a paddle brush is mandatory.
- He believes he can fill the role of rangy wing scorer that seems almost mandatory for championship teams.
- "Self-deprecation is mandatory here", he said.
Compulsory: 1060 cases
- compulsory health insurance
- states that prohibit compulsory unionism
- compulsory celibacy for the clergy
- added to the school curriculum as a compulsory second language
- U.S. imperialism can be thought of as a system of compulsory heterosexuality
- My landlord and mother made my weekly visits to the center compulsory if I was to continue running my business rent free from her basement.
Obligatory: 808 cases
- the obligatory happy ending
- when the obligatory compliments were out of the way
- I would hang up on my father after the obligatory five minutes
- the laptop computer has become nearly obligatory on campus
"Mandatory" is presumably related to "mandate" and used when it's a matter of law or regulation.
"Obligatory" is presumably related to "obligation" and used when it's a matter of moral, social or other obligation rather than law. (Like "the obligatory happy ending".)
"Compulsory" seems to mean that you are forced to do something, but the forcing mechanism is unspecified?
Is this approximately correct, and are there other rules of thumb for when to use which term?
There seems to be some cases where the terms are interchangeable: "Mandatory health insurance" and "compulsory health insurance" would be equally acceptable, wouldn't it?
Would "school curriculum compulsory second language" read the same if we substitute "mandatory" or "obligatory"?
Solution 1:
I think you mostly have it right, but for further exemplification, here are the most common immediately following collocates for each these words from the COCA:
Most common collocates for mandatory
1 TESTING 151
2 MINIMUM 125
3 RETIREMENT 107
4 MINIMUMS 100
5 REPORTING 87
6 SENTENCES 78
7 EVACUATION 74
8 SENTENCING 74
9 DISCLOSURE 63
10 ARBITRATION 56
11 SPENDING 41
12 DRUG 36
13 SENTENCE 35
14 EVACUATIONS 32
15 ARREST 27
16 PRISON 27
17 COUNSELING 26
18 OVERTIME 24
19 RECYCLING 23
20 BUSING 22
21 SANCTIONS 22
22 INSURANCE 21
23 SERVICE 21
24 HIV 20
25 RELEASE 20
Most common collocates for compulsory
1 EDUCATION 86
2 MILITARY 53
3 SCHOOL 31
4 SCHOOLING 21
5 STERILIZATION 19
6 LICENSING 18
7 ATTENDANCE 18
8 NATIONAL 16
9 SERVICE 15
10 MILITIA 14
11 MEMBERSHIP 14
12 JURISDICTION 11
13 HEALTH 11
14 HETEROSEXUALITY 10
15 LABOR 10
16 ARBITRATION 9
17 LICENSE 9
18 FIGURES 9
19 PROCESS 9
20 PUBLIC 9
21 RETIREMENT 8
22 DISPUTE 7
23 ARMY 7
24 VOTING 6
25 INSURANCE 6
Most common collocates for obligatory
1 SERVICE 10
2 NATURE 8
3 STOP 8
4 REFERENCE 6
5 STRUCTURE 5
6 CELIBACY 4
7 EXCHANGE 4
8 VISIT 4
9 READING 4
10 MILITARY 4
11 QUESTION 4
12 SLAP 3
13 NOD 3
14 RETURNS 3
15 BASIC 3
16 PERIOD 3
17 UPON 3
18 PHOTO 3
19 BOOK 3
20 EARLY 3
21 PARTHENOGENESIS 2
22 PREPOSITION 2
23 PILGRIMAGES 2
24 HAGGLING 2
25 ALTRUISTIC 2
As you can see, mandatory and compulsory have much stronger collocates. The collocates for mandatory are more things that are simply required by law, policy, or rule, whereas compulsory is more for specifically things that someone must do (e.g. education, military, sterilization). Obligatory, on the other hand, doesn’t have much of a strong affinity for certain things, and can be used generally for anything that is required by social custom.