Verb Stems and Endings: How Korean Conjugation Works

Almost everything you will ever learn about Korean verbs runs on one small machine, and this page builds it. Once you understand that a Korean verb is a fixed stem plus a stack of peelable endings, the language stops looking like a wall of unrelated forms and starts looking like what it actually is: strikingly regular. Learn the machine here, and every later page is just a new ending to slot in.

Every verb is cited in a -다 form

Open any Korean dictionary and every verb and adjective is listed in a form ending in -다: 가다 ("to go"), 먹다 ("to eat"), 좋다 ("to be good"). This -다 is the dictionary form (사전형) — a naming label, the way English lists verbs as "to go, to eat." It is not a sentence. This is the first thing to internalize, because the single most common beginner error is trying to speak in dictionary forms.

The -다 form 가다 never means "I go" in speech. It means "the verb to go," a citation. To actually say something, you strip the -다 and build a real form.

The stem: strip the -다

Remove -다 and what remains is the stem (어간) — the unchanging core that carries the meaning:

The stem is a workbench, not a word. You never say a bare stem out loud (×가, ×먹). Its whole job is to receive endings. And here is the payoff for an English speaker: unlike go / went / gone, the Korean stem does not change. 먹- stays 먹- across present, past, future, polite, casual — you only change what you hang off the end of it.

Conjugation = attaching endings to the stem

To conjugate is simply to take the stem and add one or more endings (어미). The polite present is the ending -아/어요:

That last example is worth pausing on: 좋다 is an adjective in English terms, yet it conjugates with the same -아/어요 ending as 가다. In Korean, adjectives are a kind of verb (a descriptive verb) and run through this exact same machine — a fact that reorganizes a lot of English intuitions, covered on action verbs vs descriptive verbs.

Endings stack in a fixed order

The real power appears when you stack endings. They go on in a fixed sequence: tense first, then politeness/mood last. The past-tense marker is -았/었-, and it slots in before the politeness ending:

Read 먹었어요 left to right and you can see the layers: 먹 (eat) + 었 (past) + 어요 (polite). This is the whole system in miniature. Nothing fuses beyond recognition; you peel the ending off and the past marker is right there, and under it, the stem.

The one distinction that governs everything: vowel vs consonant stems

Here is the single fact that decides the shape of most endings you will ever meet. Look at the last letter of the stem: does it end in a vowel or in a consonant (a 받침, batchim — the bottom consonant of a syllable block)?

• Vowel stems: 가- (ends in ㅏ), 오- (ends in ㅗ), 보- (ends in ㅗ)
• Consonant stems: 먹- (ends in ㄱ), 읽- (ends in ㄺ), 앉- (ends in ㄵ)

A large family of endings is written -(으)… with the 으 in parentheses. That 으 is a little buffer vowel: a consonant stem inserts it to avoid an unpronounceable consonant pile-up; a vowel stem skips it. Watch the honorific ending -(으)세요:

The vowel stem 가- takes plain -세요 → 가세요. The consonant stem 앉- cannot say ×앉세요 comfortably, so it inserts the buffer: 앉 + 으 + 세요 → 앉으세요. Same ending, two skins, chosen purely by whether a batchim is in the way.

The same split shows up in the "if" ending -(으)면 and the prospective -(으)ㄹ:

Vowel stem 가- → 가면; consonant stem 먹- → 먹으면. You are not memorizing two separate words — you are applying one rule to a stem whose last letter you can see at a glance.

Why this makes Korean easier than it looks

Coming from English, the instinct is to memorize whole conjugated forms as if each were a new vocabulary item. Resist it. Korean rewards the opposite strategy: learn the endings as a small, closed set, and learn to read a stem's last letter. Then any of the language's thousands of verbs conjugates the moment you know its stem. Went, gone, going, goes are four unpredictable English shapes; Korean gives you one stem and a handful of stackable, meaning-transparent suffixes that behave the same on every verb. The endings are the real curriculum — the stems just plug in.

The rest of the verb system is footnotes to this page: which vowel harmony picks 아 vs 어 (see vowel harmony), a few stem classes that bend the rules (like the ㄹ-stems and the seven true irregulars), and the productive 하다 verbs. But the machine is the machine you just built.

Common Mistakes

1. Using the bare dictionary form as a spoken sentence. -다 is a citation label, not "I do X." A real utterance needs a real ending.

2. Speaking a bare stem. The stem is a workbench; it is never a word on its own.

3. Forgetting the 으 buffer on a consonant stem. A consonant stem inserts 으 before -(으) endings.

4. Adding the 으 to a vowel stem. A vowel stem skips the buffer entirely.

Key Takeaways

• Verbs and adjectives are cited in a -다 form; strip -다 to get the stem (가다 → 가-, 먹다 → 먹-).
• The dictionary form is a name, not a sentence — never say ×저는 가다.
• Conjugation = attaching endings to the stem, stacked in order: tense before politeness (먹 + 었 + 어요 = 먹었어요).
• The master distinction is vowel stem vs consonant stem: endings written -(으)… drop the 으 after a vowel (가세요, 가면) and keep it after a consonant (먹으세요, 먹으면).
• Korean is agglutinative and regular — one stable stem plus peelable suffixes, so learning the endings once unlocks every verb.