I got a letter from the health insurance company. The Korean version contained "당연가입," which corresponded to "mandatorily [sic] subscribed" in the English version.

Although my native Korean friend had never heard the term "당연가입" before, he could guess what it meant. Whenever I discussed this topic with other native Koreans, they all used the term "의무 가입." (Even though I started the conversation with 당연가입 because I did not know 의무, yet.)

Is there any difference between 당연가입 and 의무 가입? Why wouldn't the letter just say "의무 가입," which seems to be more common?

  • I think 당연가입 is legal term.
    – LegenDUST
    Jul 6, 2019 at 4:13

2 Answers 2


In my view, that is just their choice. Googling 당연가입 (about 69,000 results) and 의무가입 (about 462,000 results) indicates that Koreans use the latter more frequently.

당연한 의무 and 당연 의무 (meaning "rightful duty") are used as collocations. This is maybe the reason they use 당연 as in 당연가입. As you know, "rightful" and "duty" are related to each other:

rightful: according to what is correct or what should be done legally or morally

duty: something that you have to do because it is morally or legally right

Law terms usually have 의무 to mean something is obligatory, so people should be more familiar with it. The meaning of 당연 is not limited to moral and legal correctness. Look at these terms:

당연: 당연상인 (an actual merchant; a merchant who engages in commercial transactions in her or his own name), 당연직위원 (an ex-officio member), 당연퇴직 (rightful retirement), ...

의무: 의무보험 (compulsory insurance), 의무교육 (compulsory education), ...

As you may have noticed, people are likely to have heard and said 의무보험. It is natural for them to deem that 보험 가입 (insuring) is mandatory.


As per legal terms, 당연(當然) roughly corresponds to natural or automatic. So the term 당연가입 implies that you will be automatically subscribing to something if you meet the required conditions, regardless of your intention or action.

While 의무가입 may refer to a very similar thing in effect, this term has emphasis on the obligation, that you cannot refuse the subscription. On the other hand, 당연가입 has emphasis on the automatic nature of the subscription, and you might (or not) be able to cancel it if you wish to (depending on the terms).

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