-자
Quick answer: -자 means let us — the casual form of -(으)ㄹ까요? and 같이 해요.
How to form it
Verb stem + 자 · same form whether or not the stem ends in a consonant
In Korean: 동사 어간 + 자 받침과 상관없습니다
What to know
-자 is the casual twin of -(으)ㅂ시다 and 같이 -아/어요. Note that it is spelled the same as the verb 자다 — 자자 means «let us sleep». Only the sentence tells you which one you are looking at.
Examples
- 주말이니까 나가자.It is the weekend, so let us go out.
- 같이 놀자.Let us hang out.
- 반말로 하자.Let us drop the polite endings.
Where it's taught
HanDa Level 2 (TOPIK I), Lesson 27: 주말이니까 나가자 — It is the weekend — let us go out. Also in the Level 2 book.
Practise -자 out loud
In the HanDa app this is Level 2, Lesson 27 — drills, a speaking check and an AI teacher that corrects what you say. Free for 7 days.