“〜hitotsu ni wa・hitotsu wa”: One Reason Is / For One Thing [JLPT N2]

Content by NTJ Kuma · Nihongo to Japan editorial team · Updated July 27, 2026

A written way to list one of several reasons

「理由は、一つには時間、もう一つにはお金だ」 — listing one thing's multiple reasons one by one

「転職を考える理由は、一つには給料の低さ、もう一つには人間関係のストレスだ」 (the reasons I'm considering a job change are, for one the low pay, for another the stress of relationships) — 「一つには（ひとつには）／一つは」 is used to list one thing's multiple reasons/causes, pointing out one of them first: “one reason is …(another is …).” It often echoes 「もう一つには」. This guide covers 「一つには」's use and attachment, separating it from 「まず／第一に」 and the contrasting 「一方で」 (N2).

Core: one of the (reasons) is ～ (listing, itemizing)

「一つには〜、もう一つには〜」 = “for one (reason) …, for another …” — when a matter has several reasons/causes, using 「一つには」 to state the first, implying there are others:

• 成功の秘訣は、一つには努力を続けたことだ (one secret to success is having kept up the effort).
• 少子化の原因は、一つには経済的な不安がある (one cause of the low birthrate is economic anxiety).

Feel: “one of the (reasons) is …” — the core is “the first item when listing the many reasons/causes of one thing one by one,” implying “not just this, but others.” Often echoed by 「もう一つには (another is)」, forming “for one …, for another ….” A formal, expository expression (great for analyzing causes).

Attachment & echoing

Examples in use

• この地域が人気なのは、一つには交通の便がいいからだ。(One reason this area is popular is its good transport access.)
• 失敗の原因は、一つには準備不足、もう一つには油断だった。(The causes of failure were, for one insufficient preparation, for another carelessness.)
• 彼が信頼されるのは、一つには約束を必ず守るからだ。(One reason he's trusted is that he always keeps his word.)
• 値上げの背景には、一つには原材料費の高騰がある。(One thing behind the price rise is surging raw-material costs.)
• 参加を決めた理由は、一つには勉強のため、もう一つには人脈作りだ。(My reasons for joining are, for one to study, for another to build connections.)

⚠️ Where learners slip up

① 「一つには」 is for ‘the first item when listing reasons/causes,' often echoed by 「もう一つには」. It's itemized listing — when a matter has several causes, 「一つには」 states the first, implying “there are others,” so it often comes in pairs (一つには〜、もう一つには〜). Stating only one with 「一つには」 leaves the listener waiting for the next. If you have only one reason and won't list, just say 「原因は〜だ」, not 「一つには」. Use it only to “list several reasons one by one.”

② 「一つには」 (listing reasons) ≠ 「一方で」 (contrasting facts). Both might touch “on one hand” in translation, but differ in use. 一つには = one of the (reasons) is ～ (listing several same-direction reasons) (原因は一つには〜、もう一つには〜 = the causes are, for one …, for another …); 一方で = on the other hand (contrasting two coexisting, often opposing facts or facets) (仕事は順調だ。一方で、家庭がおろそかになっている = work is going well; on the other hand, home is being neglected; see 〈反面／一方で〉). 一つには lists “causes” (same direction), 一方で contrasts “facts/facets” (opposing). Don't confuse “listing one of the reasons” with “contrasting the other side.”

③ 「一つには」 vs 「まず／第一に」 differ slightly in feel. Both can list, but 「まず／第一に」 leans ‘first in order' (firstly, first) (まず〜、次に〜 = first …, then …); 「一つには」 leans ‘one of the (parallel) reasons,' not stressing order, just “one (of many).” For “firstly (first step/point)” use まず／第一に; for “one of the (reasons)” use 一つには. 「一つには」 especially suits analyzing causes, reasons (原因は一つには…) in exposition.

🔄 Compare: 一つには／もう一つには／まず・第一に／一方で

💡 The one thing to remember

「一つには（ひとつには）／一つは」 = one of the (reasons/causes) is ～, its core “the first item when listing a matter's several causes one by one,” implying “not just this, but others,” often echoed by 「もう一つには」 (原因は一つには〜、もう一つには〜). Three points: ① it's listing, itemizing — often in pairs; stating only one with it leaves the listener waiting; ② tell it from 「一方で」 — 一つには lists “causes” (same direction), 一方で contrasts “facets” (opposing; see 〈反面〉); ③ slightly different from 「まず／第一に」 — the latter stresses order (firstly), 一つには is “one of the (parallel reasons),” especially suited to analyzing causes in exposition. To clearly list, one by one, “a matter's several causes,” 一つには is the handiest.

❓ Common questions

Q: 「一つには」 and 「まず／第一に」 both list — how do I tell them apart?

Whether it ‘stresses order' or ‘one of the parallel reasons.' 「まず／第一に」 = firstly／first (stressing ‘first in order, in steps,' often followed by 「次に／第二に」): 料理はまず野菜を切る。次に、肉を炒める (in cooking, first cut the vegetables; then fry the meat — stressing step order); 理由は第一に安全性、第二に価格だ (the reasons are, first safety, second price — stressing ranking). It has a “first step, first point” order feel. 「一つには」 = one of the (reasons) is ～ (listing one of ‘several parallel causes,' not stressing which comes first, just ‘one of them'): 人気の理由は、一つにはデザイン、もう一つには価格だ (the reasons for its popularity are, for one the design, for another the price — two parallel reasons, no order). It has an “one (of the many reasons)” itemizing feel, especially for analyzing causes, reasons. Test: to stress ‘order, steps (first, second …)' → まず／第一に; to list ‘one of the (parallel) reasons/causes' → 一つには (with もう一つには). So for steps and rankings use 「まず・第一に」; when analyzing “what causes a matter has,” list them one by one with 「一つには〜、もう一つには〜」. The latter is especially idiomatic in expository writing and cause analysis.

Q: 「一つには」 and 「一方で」 both seem to say ‘one … the other …' — how do I tell them apart?

Wholly different: 「一つには」 lists ‘same-direction reasons,' 「一方で」 contrasts ‘two opposing facets/facts.' 「一つには〜、もう一つには〜」 = one of the (reasons) is ～, another is ～ (listing a matter's several ‘reasons/causes,' which are ‘same-direction, parallel,' all explaining why the same thing): この計画が失敗したのは、一つには資金不足、もう一つには計画の甘さだ (this plan failed, for one due to lack of funds, for another due to a naive plan — both are “causes of failure,” same-direction and parallel). It “itemizes several causes.” 「一方で」 = on the other hand (contrasting ‘two coexisting, often opposing or contradictory' facts/facets): この薬は効果が高い。一方で、副作用も強い (this medicine is effective; on the other hand, its side effects are strong too — “effective” and “strong side effects” are two opposing sides); 都会は便利だ。一方で、生活費が高い (the city is convenient; on the other hand, the cost of living is high). It “contrasts a matter's positive/negative or differing two sides” (see 〈反面〉). Test: listing ‘several same-direction causes' → 一つには (all explaining “why”); contrasting ‘two opposing facets' → 一方で (one good one bad/two opposing sides). E.g., 「原因は一つには〜、もう一つには〜」 (listing causes) vs 「便利だ。一方で高い」 (contrasting two sides). One lists causes, one contrasts facets — wholly different directions.

🖊️ Practice Questions (5)

Q1. 「成功の秘訣は、___努力を続けたことだ。」(one of the secrets is)

(A) 一つには　(B) たとえ　(C) まるで　(D) どうせ

Q2. 「一つには」とよく一緒に使うのは?

(A) もう一つには／もう一つは

(B) ところで

(C) しかし

(D) ぜひ

Q3. 「原因は一つには準備不足だ」の意味は?

(A) One of the causes is lack of preparation (implying there are others)

(B) The only cause

(C) No cause

(D) Unrelated to preparation

Q4. 「一つには」が使われる場面は?

(A) Pointing out the first item when listing multiple causes/reasons

(B) Indicates concession

(C) Indicates time

(D) Indicates command

Q5. 用法が自然なのは?

(A) 一つには費用、もう一つには時間の問題だ。　(B) 一つには行く。

(C) 一つにはを食べる。　(D) 一つにはだ高い。

Answer Explanations

1. (A) 一つには ── one of the secrets is.

2. (A) ── often paired with もう一つには.

3. (A) ── one of the causes (implying there are others).

4. (A) ── points out the first item when listing causes.

5. (A) ── 「一つには〜、もう一つには〜」 is correct.