Haeyo vs Hamnida (해요 vs 합니다): Which Ending Do I Use?

해요 covers most of your life, and you should learn it first. The three endings are not politeness turned up and down. Each one records what you are to the person you are speaking to, which is why the same sentence in the wrong one is not rude so much as strange.

The order courses usually teach them in is the opposite of the order you need them in, which is where the confusion starts.

The three, on one verb

1. 가 (banmal). Close friends of the same age, younger family, and nobody else. Not a stranger, ever, regardless of how friendly the moment feels.
2. 가요 (haeyo). Almost everything. A shop, a colleague, a taxi, a teacher, somebody older you are not close to.
3. 갑니다 (hamnida). Formal and public, and note that somebody older is not automatically this. An elder you are not close to usually gets 해요 with 시 on the verb (가세요), not 갑니다. Announcements, presentations, the military, a service worker speaking to a customer, a first meeting with somebody important.

Notice that the middle one is doing most of the work. That is not a simplification for beginners, it is what adults use with each other all day.

Why it is not a politeness dial

If it were a dial, using a higher setting would always be safer. It is not. 갑니다 to a friend is not extra polite, it is a joke or a distance you just put between you.

What the ending encodes is the relationship, and a relationship that both people can see. Getting it wrong upward reads as coldness. Getting it wrong downward reads as presumption. Neither is a matter of degree.

The one place hamnida is not optional

Set greetings. A handful of fixed expressions are locked in the formal form and almost nobody swaps them into 해요, even in an otherwise casual conversation.

These are not you choosing a level. They are whole expressions that happen to be built that way, and learning them as units saves you from deciding anything.

This is also why mixing sounds fine in real conversations: a formal set greeting followed by 해요 for the actual talking is the normal shape, not a slip.

Where learners get caught

• Dropping to 반말 because the mood is friendly. Warmth is not the trigger. Relationship and age are. A friendly stranger is still a stranger.
• Staying in 합니다 to be safe. Two hours of it with somebody who used 해요 back at you reads as keeping distance.
• Learning 합니다 first because a course opened with it. Then having no ending for ordinary life, which is where every conversation you actually have takes place.

What to do about being asked to drop it

You will be told 말 놓으세요, which means "speak comfortably" and is an invitation into 반말. It is a real offer and refusing it politely is also fine.

The safe move is to drop one notch and see. Going straight from 갑니다 to 가 in one step is what feels abrupt, not the change itself.

What to do this week

1. Put everything in 해요 for now. It is correct in almost every situation you are in and it is never offensive.
2. Learn the three fixed greetings above as whole units, not as examples of a level.
3. For each person you speak Korean to this week, say out loud which of the three they get and why. The answer is almost always the middle one.
4. Leave 반말 alone until somebody offers it. There is no situation where you need it and being without it costs you nothing.

The short version

해요 covers most of your life. 합니다 is for formal settings and a few fixed expressions. 반말 is for people you are already close to, and waiting to be invited into it is normal rather than timid.

Read next

• Textbook Korean vs Real Korean: How Do I Stop Sounding Like a Book?
• Can You Learn Korean from K-Dramas?