What is a 받침 and why does it matter?

A 받침 (batchim) is a final consonant at the bottom of a Korean syllable block. Many particles have two forms, and the choice between them depends entirely on whether the preceding noun ends in a batchim (consonant) or in a vowel. Picking the wrong alternant sounds clearly ungrammatical.

What is the difference between 은/는 and 이/가?

은/는 is the topic marker, framing what the sentence is about and often implying contrast, while 이/가 is the subject marker that identifies the doer, frequently with new information. The two-form split within each pair is purely phonological: 은 and 이 follow consonants, 는 and 가 follow vowels.

How do I choose between 을 and 를?

을 and 를 both mark the direct object. Use 을 after a noun ending in a consonant and 를 after a noun ending in a vowel. For example 밥을 (rice + object) but 사과를 (apple + object). The rule is the same consonant-versus-vowel test used by the other paired particles.

Does 으로/로 follow the same rule?

Almost. 으로 attaches to consonant-final nouns and 로 to vowel-final nouns, but there is one exception: nouns ending in the consonant ㄹ (rieul) take 로, not 으로. So 손으로 (with the hand) but 칼로 (with a knife), because 칼 ends in ㄹ.

Are all Korean particles paired?

No. Some particles such as 의 (possessive), 에 (location/time), 에서 (from/at), 도 (also), and 부터/까지 (from/until) have a single form regardless of the preceding sound. Only a handful of high-frequency particles have the consonant/vowel alternation, but those are the ones learners use constantly.

Korean Particle (조사) Reference

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Korean attaches particles (조사, josa) after nouns to mark their grammatical role. Several of the most common particles come in two forms, and which one you use depends on whether the noun ends in a consonant (a 받침, batchim) or a vowel. This tool explains each particle and automatically picks the right alternant for any Hangul noun you type.

How it works

The rule is phonological. For each paired particle:

noun ends in a consonant (받침)  →  use the "consonant" form
noun ends in a vowel             →  use the "vowel" form

The major pairs:

은 / 는     topic marker        (책은 / 사과는)
이 / 가     subject marker      (책이 / 사과가)
을 / 를     object marker       (책을 / 사과를)
와 / 과     "and / with"        consonant→과, vowel→와
으로 / 로   "by / to / with"    + exception: ㄹ-final takes 로

To detect a 받침, the tool decomposes the last Hangul syllable: each modern syllable block is computed as 0xAC00 + (initial × 588) + (medial × 28) + final. If the final index is non-zero the syllable ends in a consonant. The particle 으로/로 adds one twist — a noun ending in ㄹ takes 로, not 으로.

Example and notes

책 (book) ends in the consonant ㄱ, so it takes the consonant forms: 책은, 책이, 책을. 사과 (apple) ends in the vowel ㅏ, so it takes the vowel forms: 사과는, 사과가, 사과를. For the instrumental, 손 (hand) → 손으로, but 칼 (knife) ends in ㄹ → 칼로. Single-form particles like 의 (possessive), 에 (at/to), 에서 (from), and 도 (also) never change, so focus your memory on the paired ones, which appear in almost every sentence.