The particle "은" (eun) is a subject marker in the Korean language. It is used after a noun to indicate that the noun is the subject of the sentence. "은" is typically attached to nouns that end in a consonant, while "는" (neun) is used for nouns that end in a vowel. This distinction helps clarify the focus of the sentence. In Korean grammar, "은" plays a crucial role in sentence structure. By marking the subject, it helps listeners understand who or what is being discussed. This particle is essential for forming clear and coherent sentences in everyday conversation and writing in Korean.