dallineun geon jaemiisseo.

Running is fun.

Breakdown of dallineun geon jaemiisseo.

• 재미있다: fun
• ~은: topic particle
• 달리다: to run
• 것: thing

Questions & Answers about dallineun geon jaemiisseo.

What does 달리는 건 literally mean and how is it formed?

달리는 건 comes from the verb 달리다 (“to run”). Here’s the breakdown:

• 달리- is the stem of 달리다.
• -는 turns the verb into its present–attributive (relative) form, like “running.”
• 것 means “thing” or “act,” so 달리는 것 is “the act of running.”
• -은 is the topic marker, making 달리는 것은 (“as for running”).
  In casual speech, 것은 often contracts to 건, giving 달리는 건.

Why is 것은 contracted to 건 here?

In spoken Korean, 것은 frequently becomes 건 to sound more natural and concise. The contraction happens because:

• 것 + 은 → 것은
• Rapid pronunciation slurs 것은 into 건
  This is common in informal contexts (반말).

Why do we use -는 before 것? What role does -는 play?

The ending -는 is the present–attributive form (현재형 관형사형) of a verb. It allows the verb to modify a noun:

• 달리다 (to run) → 달리는 (running)
  By saying 달리는 것, you treat “running” as a noun phrase (“the act of running”). Without -는, you couldn’t link 달리다 directly to 것.

Could I use 달리기 instead of 달리는 건? How do they differ?

Yes. 달리기 is the nominalized form of 달리다 using -기 ("running" as a noun). You could say:

• 달리기는 재미있어 (“Running is fun”).
  Differences:
• 달리기 is a pure noun meaning the activity.
• 달리는 건 is a relative clause + nominalizer, slightly more descriptive (“the act of running”).
  Functionally they’re very similar in casual speech.

What’s the difference between using -은/는 and -이/가 with 것 in this sentence?

• -은/는 is the topic marker, emphasizing or framing “running” as the topic:
  달리는 건 재미있어 (“As for running, it’s fun”).
• -이/가 is the subject marker, presenting it more neutrally:
  달리는 것이 재미있어 (“Running is fun”).
  Using -은/는 can add contrast or highlight the topic, while -이/가 just states a fact.

Why is 재미있어 used instead of 재미있다?

재미있다 is the dictionary form (“to be fun”). In casual speech you drop -다 and use the informal present ending -어, so:

• 재미있다 → 재미있어

What speech level is 달리는 건 재미있어? How can I make it polite or formal?

Currently it’s informal/casual (반말). To change levels:

• Polite (해요체): 달리는 건 재미있어요
• Formal (하십시오체): 달리는 것은 재미있습니다

How do I change this sentence to past tense?

Switch the adjective ending -어 to -었어 for past informal:

• 달리는 건 재미있었어 (“Running was fun”).
  Polite past: 달리는 건 재미있었어요.

Why is there no pronoun (like “I”) in 달리는 건 재미있어?

Korean often omits subjects or pronouns when context is clear. Here, 달리는 건 itself is the topic (“as for running”), so you don’t need I or it. The sentence simply states a general opinion.