-은

Etymology 1
From, from. Attested since the very beginning of Korean writing in the first millennium. The post-vocalic form is probably formed by pre-Middle Korean reduplication, with the original form  now relegated to colloquial speech.

Particle

 * 1) what about;
 * 1) what about;
 * 1) what about;
 * 1) what about;
 * 1) what about;
 * 1) what about;
 * 1) what about;
 * 1) what about;
 * 1) what about;

Usage notes

 * can appear after bare nouns and pronouns, adverbs, certain verbal connective suffixes (e.g., ), and most case-marking particles. It is not compatible with nominative case markers and , or with accusative case marker ; if a noun in the nominative or accusative is topic-marked, the case-marking particle cannot appear.
 * The distinction between topic-marking and subject-marking  and  is often difficult for non-fluent speakers. Essentially,  is explicitly topicalizing, i.e. marking previously known information as the topic to which the new information in the subsequent statement applies, while  and  (by virtue of not being explicitly topicalizing) has a focalizing connotation, i.e. marking the preceding word as new information introduced into the discourse. Compare the context of the following:
 * Accordingly, can only be used for a topic that is already shared knowledge to both discourse participants. In the first example below, topic-marked  is ungrammatical because the identity of the person is not shared knowledge prior to the conversation. But once the presence of the older brother is shared knowledge, topic-marking can be used:
 * Similarly, the use of in statements of general fact can be explained by the fact that the existence of e.g. Korea or the sun is already common knowledge to all discourse participants.
 * Accordingly, can only be used for a topic that is already shared knowledge to both discourse participants. In the first example below, topic-marked  is ungrammatical because the identity of the person is not shared knowledge prior to the conversation. But once the presence of the older brother is shared knowledge, topic-marking can be used:
 * Similarly, the use of in statements of general fact can be explained by the fact that the existence of e.g. Korea or the sun is already common knowledge to all discourse participants.
 * Similarly, the use of in statements of general fact can be explained by the fact that the existence of e.g. Korea or the sun is already common knowledge to all discourse participants.
 * Similarly, the use of in statements of general fact can be explained by the fact that the existence of e.g. Korea or the sun is already common knowledge to all discourse participants.


 * When a topic-marked word or phrase is at the beginning of the sentence, it is most commonly intended as either the topic or the background information of the rest of the sentence. When it appears within a sentence, it is almost always contrastive or emphatic.

Etymology 2
From, from.

In Old Korean, a (perhaps the) primary function of this suffix was to form verbal gerunds that could function as nouns, much as English -forms serve as both independent nouns and to attribute nouns adjectivally; this nominalizing usage was only vestigial in Middle Korean and is wholly defunct today.

Suffix

 * 1) that, which;