Learn Hardcore Japanese: butyou ha kaigityuu ni koohii wo nomimasu. - The department manager drinks coffee during meetings.

は marks the topic of the sentence—what you’re talking about—so it signals 部長 as “the manager” or as for the manager. In contrast, が marks the grammatical subject and often introduces new information or emphasizes who is doing the action. Here we already know we’re talking about the manager, so は is the natural choice.

What’s the role of に in 会議中に? Can it be omitted?

会議中 by itself means “during the meeting,” but when you want to use it as a time expression, you usually add に to mark “at/during that time.”
You can sometimes omit に after 〜中 (e.g. 会議中コーヒーを飲みます), but including に makes the time-marker explicit and sounds more natural in polite statements.

What’s the difference between 会議中に and 会議の間に?

Both mean “during the meeting.”
• 会議中 uses the suffix 中 attached directly to 会議, making it concise.
• 会議の間 uses 間 (“interval”) with the possessive の, literally “the interval of the meeting.”
Usage-wise they’re interchangeable, though 会議中 is more common in everyday speech.

How do you pronounce 会議中 and what does 中 mean here?

会議中 is pronounced kaigi-chū (かいぎちゅう). The character 中 here means “in the middle of” or “during,” indicating that something happens within that period.

Why is コーヒー written in katakana?

コーヒー is a loanword from English coffee. In Japanese, most foreign words are written in katakana to distinguish them from native vocabulary.

Why do we put を after コーヒー?

を marks the direct object of a verb. Here コーヒー is what the manager is drinking, so コーヒーを飲みます tells us he drinks coffee.

Why is the verb in the 〜ます form (飲みます) and what does it tell us about tense or politeness?

The 〜ます form is the polite present/future tense. It shows respect toward the listener or reader. Japanese verbs in this form don’t distinguish present vs. future; 飲みます can express a habitual action (“drinks”) or a future action (“will drink”) depending on context.

Does this sentence mean he is drinking coffee right now or that he usually drinks coffee during meetings?

With 飲みます in the simple present, the sentence expresses a habitual action: “He usually drinks coffee during meetings.” If you want to say he is drinking coffee at this very moment, you would use the progressive form 飲んでいます.

Could we use the continuous form 飲んでいます here? What would change?

Yes.
• 部長は会議中にコーヒーを飲んでいます。
This indicates that the manager is in the process of drinking coffee right now during the meeting, rather than describing a habitual behavior.

Can we change the word order, for example 部長はコーヒーを会議中に飲みます?

Yes, Japanese word order is relatively flexible. Both of these are grammatical:
1) 部長は会議中にコーヒーを飲みます。
2) 部長はコーヒーを会議中に飲みます。
However, putting the time expression 会議中に before the object often sounds clearer and more natural, because it sets “when” before “what.”