Learn Hardcore Japanese: kare ha benkyousinai wake de ha nai ga, syuutyuu ga nigate da. - It’s not that he doesn’t study, but he’s not good at concentrating.

Yes, but with nuance. It implies he does study to some extent, while softening or qualifying the statement (e.g., “He does study, but…”). It often counters an assumption.

How is 勉強するわけではない different from 勉強しないわけではない?

勉強するわけではない: “It’s not (necessarily) the case that he studies.” Suggests he may not study (disclaims the positive).
勉強しないわけではない: “It’s not that he doesn’t study.” Suggests he does study somewhat (disclaims the negative). They point in opposite directions.

What’s the role of が after わけではない here?

This が is a conjunction meaning “but/however,” not the subject marker. It contrasts the first clause with what follows: “It’s not that he doesn’t study, but…”

Why is it 集中が苦手だ? Why が after 集中?

With adjectives like 好き/嫌い/得意/苦手, the thing liked/disliked/strong/weak at is marked with が. So Nが苦手だ = “be bad at N” (and often dislike it).

Could I use は instead of が in 集中は苦手だ?

Yes. 集中は苦手だ adds a contrastive/topic nuance: “As for concentration, he’s bad at it (as opposed to other things).” 集中が苦手だ is a plain statement of fact.

Is 集中が苦手だ natural, or should it be 集中するのが苦手だ?

Both are natural.

集中が苦手だ treats “concentration” as a noun concept.
集中するのが苦手だ makes the action explicit (“he’s bad at concentrating”). The second is a bit clearer/explicit.

What’s the difference between 苦手, 下手, and 不得意?

苦手: “bad at/poor at” with a sense of discomfort or dislike. Personal/subjective.
下手: “unskilled” (skill level), more objective, can sound blunt.
不得意: “not good at” (formal/literary), neutral tone.

Could I say 集中力がない instead?

Yes, but the nuance changes:

集中が苦手だ / 集中するのが苦手だ: he finds concentrating difficult (a personal weak point).
集中力がない: he “doesn’t have concentration” (sounds more absolute/harsh).

How would I make the sentence polite?

彼は勉強しないわけではありませんが、集中が苦手です。
Colloquial-soft: …わけじゃないんですが、…です。

Can I write わけ in kanji (訳)?

Yes: 訳ではない. In everyday writing both わけ and 訳 are common; kana is slightly more casual/neutral.

Can I stop the sentence after わけではない?

Yes. 彼は勉強しないわけではない。 is a complete statement (“It’s not that he doesn’t study.”). Adding が plus a second clause just gives the contrastive follow-up.

What’s the difference between わけではない, わけがない, and わけはない?

わけではない: “it’s not the case that 〜” (soft/hedging).
わけがない: “there’s no way that 〜 / impossible” (strong denial).
わけはない: literally “there is no reason/case,” but as a set phrase it’s rare; people almost always use わけがない for “no way.”

What does わけ literally mean?

It means “reason/explanation/circumstance.” In 〜わけではない, the preceding clause modifies わけ (“a reason/case where 〜”), and the whole is negated: “it’s not a case where 〜.”

Is it okay to use けど/けれど(も)/だが/でも instead of が?

Yes, with register differences:

けど/けれど(も): neutral to polite.
が: neutral/formal in writing; natural in speech.
だが: formal/literary.
でも: more conversational, starts a new sentence/clause.

How do I put this in the past?

Negate the past event inside the pattern:

彼は勉強しなかったわけではない = “It’s not that he didn’t study (then).”
For the second clause: 集中が苦手だった for past state.

Can I re-order the clauses?

Yes: 彼は集中が苦手だが、勉強しないわけではない。 Both orders are fine; you just change what you foreground first.

Do I need を in 勉強しない (as in 勉強をしない)?

No. With many する-verbs, を is optional in everyday usage: 勉強する/勉強をする. Both negatives are acceptable: 勉強しない / 勉強をしない.

What are the readings for the key words?

彼: かれ
勉強: べんきょう
集中: しゅうちゅう
苦手: にがて
わけではない: わけではない (casual: わけじゃない)

Why are there spaces in the sentence?

They’re for teaching clarity. Standard Japanese doesn’t use spaces between words: 彼は勉強しないわけではないが、集中が苦手だ。