Progressive (-고 있다)

-고 있다 attaches to a verb stem to express that an action is currently in progress. It is equivalent to the English present progressive 'be doing'. For example, 먹고 있다 means 'is eating' and 공부하고 있다 means 'is studying'.

This pattern is straightforward to form: simply add -고 있다 to the verb stem. 있다 then conjugates for tense and politeness: 있어요 (present polite), 있었어요 (past progressive), 있을 거예요 (will be doing). The past progressive 먹고 있었어요 means 'was eating'.

Some verbs in Korean already imply an ongoing state when conjugated normally. For instance, 알다 (to know) doesn't typically use -고 있다 because knowing is inherently continuous. However, for most action verbs, -고 있다 clearly distinguishes between a habitual action and one happening right now.