Learn Hardcore Korean: jeoneun mulman masyeoyo.

저는 breaks down into 저 (the humble form of “I”) + topic marker 는. It marks “as for me…” and sets you up as the topic of the sentence. We use 저 in polite speech; 나 is casual and only for close friends or people younger than you.

What does 물만 mean, and why isn’t there a separate object marker like -을/를?

만 is a particle meaning “only.” When you attach 만 to 물 (water), you get 물만 = “only water.” In colloquial Korean, 만 can replace the object marker -을/를, so you drop 을/를 and say 물만 instead of 물을만. (In very formal writing you might see 물만을, but it’s rare in speech.)

Why is the verb 마시다 conjugated as 마셔요 here?

마시다 (to drink) follows the polite present tense -아요/어요 pattern. Because 마시- ends in the vowel ㅣ, you add -어요, which contracts to -여요, giving 마셔요. This ending is informal polite, suitable for everyday conversation.

How would you say “I drink water” without implying “only”?

You’d remove 만 and restore the object marker:
저는 물을 마셔요.
This simply means “I drink water.”

What if you replace 만 with 도, as in 물도 마셔요?

도 means “also” or “too.” So 저는 물도 마셔요 means “I drink water, too.” You’ve shifted from exclusivity (only water) to inclusion (water as well as something else).

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

Korean has a Subject–Object–Verb (SOV) word order. The topic (저는), then object (물만), then verb (마셔요) is the natural order. You can’t put the verb in the middle as you would in English.

Can you drop 저는 and just say 물만 마셔요?

Yes. Korean often omits the topic or subject when it’s clear from context. 물만 마셔요 by itself can mean “I only drink water” if it’s obvious you’re talking about yourself.

How do you make this sentence more formal or more casual?

Casual/familiar: 물만 마셔. (drop 요)
Informal polite (everyday): 물만 마셔요.
Formal polite: 물만 마십니다.
Choose the ending based on your relationship with the listener and the situation.