Reason with -(으)니까 in Korean

In Brief

-(으)니까 connects a reason with a result and often corresponds to “because” or “since”: 비가 오니까 우산을 가져가세요 means “Since it’s raining, take an umbrella.” It is especially useful when the result is a command, request, suggestion, or the speaker’s judgment. Add -니까 after a vowel and -으니까 after most consonants.

Overview

Korean has more than one way to connect a cause with its result. At A2, -(으)니까 is particularly important because it does something that English “because” does not show by itself: it presents a reason as the basis for what the speaker thinks, decides, recommends, or asks someone to do. The first clause gives the reason; the second gives the conclusion or response.

For example, 시간이 없으니까 빨리 가요 can mean “Since there’s no time, let’s go quickly.” The lack of time is the speaker’s justification for the proposed action. The ending is therefore common in advice, instructions, invitations, and everyday explanations.

You may already know -아/어서, another common reason connector. The two often overlap, but -(으)니까 is the safer beginner choice before a command or suggestion. It can also sound more assertive: the speaker is explicitly putting forward a reason. English speakers should not try to assign one fixed translation to it. Depending on the sentence, “because,” “since,” “as,” or “so” may sound most natural in English.

How It Works

The basic sentence pattern

A clause is a part of a sentence built around its own verb or adjective. With -(으)니까, the reason clause comes first:

reason + -(으)니까 + result, decision, command, or suggestion

• 날씨가 좋으니까 걸어가요. — The weather is nice, so let’s walk.
• 늦었으니까 택시를 타세요. — Since you’re late, take a taxi.

Korean adjectives such as 좋다 “to be good” and 춥다 “to be cold” behave like descriptive verbs, so they take the ending directly. There is no separate word corresponding exactly to English “is.”

Choosing -니까 or -으니까

Remove -다 from the dictionary form to find the stem (the part to which an ending is attached). Then look at the stem’s final sound.

Stem ending	Form	Dictionary form	Result
Vowel	-니까	가다 “to go”	가니까
Most consonants	-으니까	먹다 “to eat”	먹으니까
ㄹ	Drop ㄹ, then add -니까	살다 “to live”	사니까
하다	하니까	공부하다 “to study”	공부하니까

The vowel/consonant distinction belongs to the Korean stem, not to the English translation. Learn the connected form aloud as a unit: 가니까, 먹으니까, 바쁘니까, 좋으니까.

Regular and common irregular changes

Some stems change shape when an ending beginning with a vowel is added. These are the same stem changes found with many other Korean endings.

Type	Dictionary form	With -(으)니까	Meaning
Regular consonant	있다	있으니까	because there is / because someone has
Regular vowel	보다	보니까	because someone sees/watches
ㄹ-ending	알다	아니까	because someone knows
ㄹ-ending	만들다	만드니까	because someone makes
ㅂ-irregular	춥다	추우니까	because it is cold
ㅂ-irregular	어렵다	어려우니까	because it is difficult
ㄷ-irregular	듣다	들으니까	because someone listens/hears
르-irregular	모르다	모르니까	because someone does not know

Do not infer every change from spelling alone; a few verbs are regular even though a similar-looking verb is irregular. For an A2 learner, it is most effective to memorize frequent combinations rather than trying to predict every verb immediately.

Nouns: -(이)니까

After a noun (a word for a person, thing, place, or idea), use the copula pattern -(이)니까, meaning “because it is…” or “since [someone] is…”.

Noun ending	Form	Example	Meaning
Consonant	-이니까	학생이니까	because they are a student
Vowel	-니까	의사니까	because they are a doctor

• 오늘은 휴일이니까 은행이 닫았어요. — The bank is closed because today is a holiday.
• 처음이니까 천천히 해도 돼요. — Since it is your first time, you can go slowly.

Tense and honorific forms

A past reason can be marked before -(으)니까:

• 늦게 잤으니까 피곤해요. — I’m tired because I went to bed late.
• 비가 많이 왔으니까 길이 미끄러워요. — The road is slippery because it rained a lot.

When the person in the reason clause deserves respectful reference, add the honorific marker -(으)시- (a marker showing respect toward the person being discussed):

• 선생님이 바쁘시니까 나중에 물어보세요. — The teacher is busy, so ask later.
• 할머니가 주무시니까 조용히 하세요. — Grandma is sleeping, so please be quiet.

The connector itself does not make the whole sentence polite. Speech level is normally shown by the ending of the final clause: compare 가, 가요, and 가세요.

Why it works with commands and suggestions

The result clause may tell someone what to do or invite people to act together:

• command: 추우니까 문을 닫으세요. — Since it’s cold, close the door.
• request: 아기가 자니까 조용히 해 주세요. — The baby is sleeping, so please be quiet.
• suggestion: 배가 고프니까 먹을까요? — Since we’re hungry, shall we eat?
• proposal: 시간이 없으니까 빨리 가요. — Since there’s no time, let’s go quickly.

This is the key practical contrast with -아/어서. In the standard beginner rule, do not use reason -아/어서 immediately before an imperative (a command) or propositive expression (a suggestion to act together). Use -(으)니까 instead.

Examples in Context

Korean	English	Note
비가 오니까 우산을 가져가세요.	Since it’s raining, take an umbrella.	Reason followed by advice or a command
시간이 없으니까 빨리 가요.	Since there’s no time, let’s go quickly.	The speaker proposes an action
배가 고프니까 먹을까요?	Since we’re hungry, shall we eat?	Suggestion with -(으)ㄹ까요?
추우니까 문 닫아.	Close the door since it’s cold.	Informal command
이 책은 재미있으니까 한번 읽어 보세요.	This book is interesting, so try reading it.	Recommendation based on judgment
내일 시험이 있으니까 오늘 공부해야 해요.	I have an exam tomorrow, so I have to study today.	Reason for an obligation
길이 복잡하니까 지하철을 탑시다.	The roads are congested, so let’s take the subway.	Formal-style proposal
아이가 자니까 조용히 말해 주세요.	The child is sleeping, so please speak quietly.	Polite request
어제 늦게 잤으니까 지금 피곤해요.	I’m tired now because I went to bed late yesterday.	Past event as the reason
처음이니까 실수해도 괜찮아요.	It’s your first time, so it’s okay to make mistakes.	Noun + -이니까
의사니까 잘 아실 거예요.	Since they’re a doctor, they’ll probably know well.	Vowel-final noun + -니까
이 문제는 어려우니까 같이 풀어요.	This problem is difficult, so let’s solve it together.	ㅂ-irregular 어렵다 → 어려우니까
저는 매운 음식을 못 먹으니까 안 매운 것으로 주세요.	I can’t eat spicy food, so please give me something mild.	Explaining a request
이미 표를 샀으니까 걱정하지 마세요.	We already bought the tickets, so don’t worry.	Past reason plus negative command

Common Mistakes

Adding the wrong variant after a consonant

• Wrong: 먹니까 배가 불러요.
• Right: 먹으니까 배가 불러요.
• Why: 먹- ends in the consonant ㄱ, so it takes -으니까.

Keeping ㄹ before -니까

• Wrong: 알니까 설명하지 마세요.
• Right: 아니까 설명하지 마세요.
• Why: A stem-final ㄹ drops before -니까: 알다 → 아니까, 살다 → 사니까.

Treating a noun like a verb stem

• Wrong: 학생으니까 매일 공부해요.
• Right: 학생이니까 매일 공부해요.
• Why: Consonant-final nouns use -이니까, not -으니까. The 이 comes from the Korean copula, the equivalent of “to be” in this structure.

Using -아/어서 before a command

• Awkward for the intended reason: 비가 와서 우산을 가져가세요.
• Natural: 비가 오니까 우산을 가져가세요.
• Why: When the result is a command or recommendation, the standard learner pattern uses -(으)니까. -아/어서 is better learned first with factual results such as 비가 와서 길이 젖었어요 “The road got wet because it rained.”

Making the reason sound more objective than it is

• Potentially too strong: 제가 바쁘니까 지금 전화하지 마세요.
• Softer alternative: 지금 좀 바빠서 나중에 전화해 주세요.
• Why: -(으)니까 can foreground your reason as justification. That is grammatically correct, but a softer explanation with -아/어서 may be more tactful when your own situation inconveniences another person.

Adding politeness to the connector alone

• Wrong idea: -(으)니까 is automatically polite.
• Correct contrast: 추우니까 닫아 / 추우니까 닫아요 / 추우니까 닫으세요
• Why: The final ending sets the speech level. The same reason connector can appear in casual, polite, or formal speech.

Usage Notes

-(으)니까 compared with -아/어서

Both forms can give a reason, and in plain statements either may sometimes be possible. The difference is often about how the speaker frames the connection, not simply about dictionary meaning.

Situation	Usually preferred	Example
Command, request, or suggestion follows	-(으)니까	늦었으니까 택시를 타세요.
Speaker’s conclusion or justification	-(으)니까	비싸니까 사지 않을 거예요.
Neutral cause and result	often -아/어서	비가 와서 길이 젖었어요.
Apology or conventional expression	often -아/어서	늦어서 죄송합니다.

English “because” does not force you to reveal this distinction, so translating from English word by word is unreliable. First decide what the second clause does. If it asks, advises, commands, or proposes, -(으)니까 is normally the clear choice.

Word order and omitted subjects

The reason normally comes before the result in this construction. Korean also leaves out a subject when context makes it clear. In 배가 고프니까 먹을까요?, the people who are hungry and the people who might eat are understood from the conversation. An English translation often has to supply “we,” even though Korean does not.

Strength and social tone

There is nothing rude about -(으)니까 itself. However, a sentence can feel forceful when the speaker states a personal reason and follows it with a direct command. Soften the final clause when appropriate:

• 기다리세요 — Please wait. (instruction)
• 기다려 주세요 — Please wait for me/us. (request)
• 기다려 주시겠어요? — Would you wait, please? (more indirect)

Grammar and politeness work together; choosing the correct connector does not remove the need to choose a suitable final ending.

Beyond the Basics / Advanced Use

You do not need to master the following uses at A2, but they explain sentences you will meet later.

Discovery: “when I did…, I found…”

-니까 does not always mean “because.” It can introduce a situation discovered after performing an action:

• 집에 가니까 아무도 없었어요. — When I got home, I found that nobody was there.
• 창문을 여니까 바람이 시원했어요. — When I opened the window, the breeze felt cool.

Here, going home did not cause everybody to be absent, and opening the window did not cause the breeze to be cool. The first action created the occasion for the speaker to notice the second fact. Context usually makes this “when/upon doing” reading clear.

-(으)ㄹ 테니까: intention or confident expectation

A common later pattern combines -(으)ㄹ 테다 with -니까:

• 제가 요리할 테니까 좀 쉬세요. — I’ll cook, so get some rest.
• 곧 비가 올 테니까 우산을 가져가세요. — It will probably rain soon, so take an umbrella.

This can present the speaker’s intention (“I’ll…”) or a confident expectation (“It will probably…”), followed by a response based on it. Learn -(으)ㄹ 테니까 as its own pattern rather than trying to build every meaning from the beginner rule.

Answering “why?” with -니까

In conversation, the reason may stand alone when the result is already understood:

• 왜 안 가요? — Why aren’t you going?
• 피곤하니까요. — Because I’m tired.

The polite final -요 is added to the connected form. This answer can sound firm or matter-of-fact. Depending on tone and context, 피곤해서요 may sound more like a neutral explanation.

Practice Tips

1. Sort by the second clause. Take ten reason sentences and mark each result as fact, command, request, or suggestion. Choose -(으)니까 first for the last three categories. This trains usage rather than simple translation.
2. Drill contrasting stem shapes aloud. Practice pairs such as 가니까 / 먹으니까, 바쁘니까 / 좋으니까, and 아니까 / 만드니까. Saying the complete form helps the sound changes become automatic.
3. Build one reason into several responses. Start with 비가 오니까… and finish it with 우산을 가져가세요, 집에 있을까요?, and 차로 가요. This makes the connector useful in real conversation instead of memorized as an isolated ending.

Related Concepts

• Prerequisite: Reason with -아/어서 — compare the more neutral cause-and-result connector and learn why commands and suggestions favor -(으)니까.