Learn Hardcore Japanese: asagohan wo tabenai to, butyou no nagai hanasi ni syuutyuu dekinai. - If I don't eat breakfast, I can't concentrate on the manager's long talk.

を marks the direct object of the verb 食べる (“to eat”). In this sentence, 朝ご飯 is what you eat, so it takes を. が would mark the subject or emphasize the noun, which doesn’t fit here.

What does the ないと in 食べないと mean? Is it “must”?

Here 食べないと is the conditional pattern (Verb-ない) + と, meaning “if you don’t…”. It’s not “must” by itself. It expresses “if you fail to eat breakfast, then…” The sense of “must eat” comes only when 食べないと stands alone as an obligation (like “I have to eat”), but with a following clause it’s conditional.

How is ～と different from other conditionals like ～たら, ～ば, or ～なら?

• ～と: describes a natural or inevitable consequence. You can’t avoid it once the condition is met (or unmet, when negative).
• ～たら: more flexible; “when/if” with past connotation, can be hypothetical.
• ～ば: “if” in written or polite speech; neutral.
• ～なら: “if” based on assumption or topic; emphasizes context.
In our sentence, ～と fits best because not eating breakfast automatically prevents concentration.

Why is there a comma after 食べないと? Is it necessary?

The comma signals a pause between the conditional clause (食べないと) and the result clause (集中できない). It’s not strictly required but helps readability, especially in written Japanese where long sentences can get hard to parse.

In 部長の長い話, why do we have two の-connected nouns and an adjective in between?

• The first の (after 部長) is the possessive/genitive: “the manager’s.”
• 長い is an い-adjective modifying 話 (“long talk”).
So the structure is: [Possessor の Noun] + [Adjective] + [Head Noun] = “the manager’s long talk.”

Why is に used in 話に集中できない?

With the verb (suru-verb) 集中する (“to concentrate”), the thing you concentrate on takes に. So 話に集中する means “to concentrate on the talk.”

What does 集中できない literally mean?

It’s the potential form of 集中する, i.e. 集中できる = “can concentrate.” With the negative 集中できない, it means “cannot concentrate.”

Can you say this sentence in polite form?

Yes. Simply make the verbs polite:
朝ご飯を食べないと、部長の長い話に集中できません。
That switches できない → できません. If you want the entire conditional more politely, you could also say 朝ご飯を食べなければ、… but that’s slightly more formal.