Subject particle (~subject)

English speakers often think of subjects as simply "who is doing the action," and they assume the subject is always the main topic of the sentence. But Korean works fundamentally differently: 이/가 doesn't just mark the subject—it *highlights* what is new, specific, or the focus of the sentence. This is a key mindset shift.

In English, you say *"A cat is sleeping"* and the subject is inherently the main idea. In Korean, 고양이가 자고 있어요 can mean the same thing, BUT the particle 가 is actually saying: "It is the cat (specifically, not something else) that is sleeping." The focus is on what is doing the action, not just stating a fact.

Here's the crucial difference: English uses word order and context to convey focus. Korean uses particles. When you use 이/가, you're emphasizing or introducing that noun as the specific answer to an implied question like "What is...?" or "Who is...?" In contrast, 을/를 (object marker) and 은/는 (topic marker) convey different information relationships. The 이/가 particle is restrictive and specific—it narrows down possibilities rather than just labeling a general topic.

Think of it this way: 이/가 asks "Which one?" while 은/는 asks "As for the topic..." English doesn't really distinguish these grammatically, so learners must actively rewire their thinking to see subjects as either newly introduced or specifically highlighted versus topics being discussed.