This expression is used to indicate that the action in the following clause occurs just after the completion of the action in the preceding clause.

It is mainly used in written language and only attaches to verbs.

Details

This expression is used when the situation in the preceding clause is the cause or motivation for some resulting state of affairs stated in the following clause. It is mainly used in written language and only attaches to verbs.

날이 어두워지자 북적거렸던 상가 안이 한산해졌다.

As soon as it became dark, the inside of the bustling shopping area emptied of people.

회사에 대한 안 좋은 소문이 나자 그 회사의 주가가 폭락했다.

As soon as a negative rumor emerged about the company, its stock plummeted.

While the expressions -자 and -자마자 are interchangeable to the extent that they both indicate that some action occurs immediately after another action ends, the two expressions have the following differences.

Kimchi Reader

Indicates that the second action occurs as or when the first action is happening.

Details

Usage

자 (Suggestion) is used to make informal suggestions to do something together. The more formal version of this expression is (으)ㅂ시다 (Suggestion).

자 (Simultaneous action) indicates that the second action happens as or when the first action is occurring. Unlike 자마자 (As soon as), which emphasizes that the second action happens immediately after the first, V-자 in this usage conveys that the two actions are closely connected in time, often overlapping.

Note: This usage of 자 is more common in written or formal contexts and is less frequently used in spoken Korean. In conversational Korean, (으)니까 (Reason or cause) or 아/어서 (Reason or cause) might be used instead.