We often talk about not a single event, we often talk about a sequence of events. Koreans are no different so there are a few ways to express how a sequence of events happened and the Korean time expression -자마자 is one of those ways.
-자마자 is a simple way to express one event or action takes place immediately after the end of another event or action. It is highly similar to another form, -고 나서, though they are not exactly the same. The main difference between the two is the timeline they express. When you use -자마자, you indicate that immediately after the end of an action or event, you did something. However, with -고 나서 you indicate you did something after you did something else. But, the follow-up action doesn’t necessarily have to happen right after your initial action. It is a slight difference in nuance between the two.
가: 수업 후에 뭐 해요?
나: 수업 후에 집에 오자마자 자요.
A: What do you do after class?
B: I sleep as soon as I get home after class.
How To Use
The verb ending -자마자 is very simple to use with verbs. To use it, you simply take the verb stem and connect it with the verb ending. There is little else to it. As an added bonus, you needn’t worry over the Korean irregular verbs as they typically do not act up with this verb ending. It is one of those easy Korean grammar topics that do exist.
Furthermore, unlike -고 나서 where the subject in both clauses has to be the same, the subject needn’t be the same for -자마자. The subject in the first and second clause can be different. However, keep in mind that the tense of a sentence is only expressed in the second clause of the sentence. You do not use tense markers with the form -자마자.