Learn Hardcore Korean: samusireseo jeomsimeul meogeoyo.

에서 marks the location where an action takes place. In this sentence, it tells you that the action (eating lunch) happens at the office. Without 에서, you wouldn’t know where the action occurs.

Why is there a 을 after 점심?

점심 means lunch. 을 (or 를 after a vowel) is the object-marking particle. It shows that 점심 is the thing being eaten by the verb 먹어요.

Why is the verb 먹어요 at the end of the sentence?

Korean normally uses Subject-Object-Verb (SOV) word order. Location or time phrases like 사무실에서 usually come first, and the verb comes last. So you get:
사무실에서 (location) + 점심을 (object) + 먹어요 (verb).

What tense and politeness level is 먹어요?

먹어요 is present tense in the polite-informal register (often called “yo-form”). It’s friendlier than the formal 먹습니다 but still polite enough for everyday conversation or speaking with strangers.

Why is the subject “I” missing?

Korean frequently omits subjects when they’re obvious from context. Here, it’s clear that the speaker (“I”) is eating lunch, so you don’t need 저 or 제가. If you really wanted to emphasize the subject, you could say 제가 사무실에서 점심을 먹어요, but that sounds redundant in most situations.

Can I say 사무실에서 점심 먹어요 without 을?

Yes. In casual spoken Korean, native speakers often drop the object particle 을/를. The meaning stays the same (“I eat lunch at the office”), but for learners it’s helpful to include particles to understand each word’s role.