Learn Hardcore Korean: jeonyeoge chinguwa keopireul masyeoyo. - I drink coffee with a friend in the evening.

In Korean, 에 is the particle that marks a point in time when something happens. 저녁 means “evening,” so 저녁에 literally means “in the evening” or “at evening.” Whenever you want to say “at 3 o’clock,” “on Monday,” or “in the morning,” you similarly add 에 (e.g. 3시에, 월요일에, 아침에).

What is the role of 와 in 친구와?

와 is the particle meaning “with.” It attaches to words ending in a vowel.

If a noun ends in a consonant, you use 과 instead (e.g. 선생님과).
In casual speech, many Koreans prefer 랑 (친구랑) or 하고 (친구하고), but 와/과 is more formal or written.

Why is 커피 followed by 를?

를 is the object marker (after a vowel-ending noun). It tells us that 커피 is the direct object of 마시다 (“to drink”). If the noun ends in a consonant, you would use 을 instead.

Why is the subject missing, and who is drinking the coffee?

Korean often omits subjects when they’re understood from context. Here, because of the polite ending -요, the default assumption is “I.” If you needed to be explicit, you could say:
저는 저녁에 친구와 커피를 마셔요.
(“I drink coffee with a friend in the evening.”)

How do we get 마셔요 from 마시다?

마시다 is a ㅅ-irregular verb. When you add a vowel-starting ending like -아요/-어요, the final ㅅ drops. So:
마시 + 어요 → 마셔요
This is the polite present tense form, meaning “(I) drink” or “(we) drink.”

Can I change the word order, for example putting 친구와 before 저녁에?

Yes! Korean word order is flexible as long as you keep the particles. Typical order is Time → Manner/Companion → Object → Verb, but you could say:

친구와 저녁에 커피를 마셔요.
Both sentences mean the same; you’re just shifting emphasis.

Is there any nuance difference between 친구와 and 친구랑?

They both mean “with a friend,” but:

친구와 feels more formal or written.
친구랑 is very common in everyday conversation and sounds more casual.

Can I drop the object marker 를 and just say 커피 마셔요?

In casual speech, Koreans sometimes omit 를 when context is clear (e.g. 저녁에 친구랑 커피 마셔요). However, keeping 를 is more precise and always grammatically correct, especially in writing or formal situations.