Meaning & Usage
✨ Basic Meaning
Expressing an expectation or inference based on someone’s known personality, character, or usual behavior.
🎯 Primary Function
To predict or assume the outcome of a situation based on the established nature of a specific person (or sometimes a group/organization). It implies a strong sense of certainty or predictability.
📋 Grammar Structure
[Noun (usually a person’s name, group, or a word describing their character)] のことだから
🎭 Usage Contexts
Formal Situations
Generally not used in highly formal or business writing/speeches, as it relies on personal knowledge/assumptions.
Informal Situations
Very common in everyday conversations among friends, family, or close colleagues.
Written Language
Appears in informal written contexts like emails, messages, or personal blogs, but less common in formal writing.
Spoken Language
Frequently used in spoken Japanese.
💡 Common Applications
Predicting positive outcomes
Used when the person is known for positive traits like diligence, kindness, or success.
Example: 彼のことだから、きっと成功するでしょう。 (Kare no koto da kara, kitto seikou suru deshou.) – Knowing him, he’ll surely succeed.
Predicting typical behavior
Used to express that someone will act in a way consistent with their known habits or character.
Example: 子どもたちのことだから、すぐにお腹をすかせるだろう。 (Kodomo-tachi no koto da kara, sugu ni onaka o sukaseru darou.) – Since they are children, they will get hungry quickly.
Expressing a natural consequence
Used when a result is a natural consequence of the person’s specific nature.
Example: 真面目な田中さんのことだから、期限内に仕事を終えるでしょう。 (Majime na Tanaka-san no koto da kara, kigen nai ni shigoto o oeru deshou.) – Since Tanaka-san is so serious/diligent, he’ll probably finish the work by the deadline.
Frequency
Moderately frequent among native speakers in appropriate contexts.
Difficulty
JLPT N2
Example Sentences
いつも一生懸命な彼女のことだから、次の試験もきっと大丈夫だろう。
Knowing how hardworking she always is, I’m sure she’ll be fine on the next exam too.
あの店の店長さんのことだから、今回も特別サービスがあるかもしれないね。
Knowing the manager of that store, there might be a special service this time too.
彼は時間に正確な人のことだから、約束の時間には来ているはずだ。
Since he is a punctual person, he should be here by the appointed time.
Notes & Nuances
📌 Important Points
Focus on the Noun’s Nature
This pattern is used when you are making an inference specifically because of *who* the person (or group) is and their established characteristics.
Example: 優しくて頼りになる山田さんのことだから、困っている人を放っておけないだろう。(Yasashikute tayori ni naru Yamada-san no koto da kara, komatte iru hito o houtte okenai darou.) – Knowing how kind and reliable Yamada-san is, he probably can’t ignore someone who’s in trouble.
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⚠️ Common Mistakes
❌ Using it for non-personal or general reasons
✅ Use standard cause/reason patterns like から or ので instead.
ことだから specifically relates the cause to the *nature* of the preceding noun (usually a person or group). It is not a general “because” pattern.
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🏛️ Cultural Context
Politeness Level: Neutral to slightly informal. It’s suitable for discussing someone in a casual or respectful way based on shared understanding of their character.
Social Situations: Primarily used when talking *about* a third person or group, or sometimes about oneself/one’s group (less common).
Regional Variations: None significant.
🔍 Subtle Differences
〜ことだから vs 〜だけに
ことだから focuses on the inherent nature or typical behavior of the subject as the reason for the prediction. 〜だけに emphasizes that something is *especially* true or expected *because* of a specific preceding condition or status (not necessarily a person’s core character).
When to use: Use ことだから when the reason for your prediction is the person’s character or typical behavior. Use 〜だけに when the reason is a specific condition, status, or effort.
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📝 Conjugation Notes
Always attaches to a Noun, usually followed by の, then ことだから.
🔊 Pronunciation Tips
Pronunciation is straightforward: Noun no koto dakara.
🧠 Memory Tips
Think of 「〜のことだから」 as meaning “Because it’s [Noun] (and you know what they’re like)…” or “Knowing [Noun]…”)
Vocabulary List
一生懸命
isshoukenmei
very hard; with all one’s might
大丈夫
daijoubu
all right; okay; safe
店長
tenchou
store manager
特別サービス
tokubetsu sa-bisu
special service
正確
seikaku
punctual; accurate
約束
yakusoku
promise; appointment
はずだ
should; expected to
Kanji List
一生懸命
いっしょうけんめい
very hard; with all one’s might
大丈夫
だいじょうぶ
all right; okay; safe
店長
てんちょう
store manager
特別
とくべつ
special
正確
せいかく
punctual; accurate
約束
やくそく
promise; appointment
宿題
しゅくだい
homework
部長
ぶちょう
department manager
細かい
こまかい
detailed; fine
違いない
ちがいない
must; without doubt
優しい
やさしい
kind
Practice Exercises
鈴木さんのことだから、きっと（ ）。
遅刻した
時間通りに来るだろう
来なかったらしい
来るはずがない
真面目な彼のことだから、この仕事は（ ）。
失敗するだろう
難しいはずだ
最後までやり遂げるだろう
途中で諦めるかもしれない
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