What Valency Change Means

Before you dive into the individual causative and passive suffixes, it pays to learn the one concept that explains what all of them actually do: valency. Valency is simply the number of core participants — arguments — a verb requires. Once you can count a verb's arguments and see how causatives add one and passives remove one, every 이/히/리/기 form on the following pages stops looking like random memorization and starts looking like a system. And in Korean, that system is visible right on the surface, because it's spelled out in particles.

Valency = how many core arguments

A verb "wants" a certain number of noun phrases to make a complete sentence:

• Intransitive verbs take one argument — just a subject. 아이가 자다 "the child sleeps." Nobody else is needed.
• Transitive verbs take two — a subject and an object. 아이가 밥을 먹다 "the child eats rice."
• Ditransitive verbs take three — a subject, an object, and a recipient. 아이가 친구에게 선물을 주다 "the child gives a gift to a friend."

Causatives ADD an argument

A causative introduces a brand-new participant — the causer, the person who makes the action happen — and pushes everyone else down a rank. Watch what happens to 자다 (one argument) when it becomes 재우다:

Two things changed at once. First, a causer appeared — 엄마가, the new subject. Second, the original subject, the one actually sleeping (아이), got demoted from subject to object: 아이가 became 아이를. The child is still the sleeper, but grammatically it's now the object of the causing. That demotion — nominative 이/가 dropping to accusative 을/를 — is the signature of causativizing a one-argument verb.

Now do it to a two-argument verb. 먹다 already has a subject and an object; causativizing it makes it ditransitive — three arguments:

Here the object 밥을 stays put, but the original subject 아이 can't become another object — 밥을 already holds that slot — so it lands as the causee, marked with the dative 에게 (or 한테 in casual speech). The three roles line up as: causer 이/가, causee 에게, object 을/를.

Passives do the OPPOSITE — they remove the agent

A passive runs the machine in reverse: it takes a two-argument transitive verb and strips out or demotes the agent, promoting the object to subject. 잡다 "catch" has a catcher and a caught; passivize it and the caught thing becomes the subject while the catcher shrinks to an optional 에게 phrase — or vanishes.

The patient 도둑 climbed from object (도둑을) to subject (도둑이); the agent 경찰 fell from subject (경찰이) to an optional 경찰에게 you could delete entirely (도둑이 잡혔어요 "the thief got caught"). So: causative = +1 argument (add causer); passive = −1 argument (drop agent). Two mirror-image operations, both realized in Korean by fused suffixes — and, awkwardly, several of the same suffixes (히, 리, 기), which is why 잡히다 can be a passive and 입히다 a causative. That overlap is untangled in the passive overview.

Why this matters more in Korean than in English

English barely reshapes its verbs for valency. "The child sleeps" vs "I put the child to sleep" just swaps in an entirely different verb phrase; "the thief was caught" just adds be + a participle. The noun phrases mostly keep their positions. Korean re-marks the nouns instead — the same participant wears 이/가, then 을/를, then 에게 depending on where the valency operation shoved it. So when you study a causative or passive, the real content isn't the suffix shape; it's which particle each noun now takes. Get the particles right and the sentence is correct even before you've perfected the verb.

Many verbs come in built-in transitive/intransitive pairs like 열다/열리다, and sorting those is its own topic — see transitive & intransitive pairs.

Common Mistakes

1. Keeping the old subject in the nominative after causativizing. Once you add a causer, the original subject must be demoted; it can't also be 이/가.

2. Double-marking the object when the causee should be 에게. With a transitive base, the object keeps 을/를, so the causee can't also take 를 — it goes to 에게.

3. Leaving the passive agent in the nominative. When you passivize, the agent is demoted to 에게/한테 — it can't stay 이/가.

4. Forgetting the object survives causation of a transitive verb. Causativizing 먹다 keeps 밥을; only the subject moves.

Key Takeaways

• Valency = the number of core arguments a verb takes (intransitive 1, transitive 2, ditransitive 3).
• Causatives ADD an argument (a causer) and demote the old subject: 이/가 → 을/를 (if the object slot is free) or → 에게 (if it's taken).
• Passives REMOVE/demote the agent, promoting the object to subject and shrinking the agent to an optional 에게 phrase.
• Korean realizes all of this by re-marking nouns with particles, so mastering causatives and passives is largely mastering which particle each noun now wears.