JapaneseJLPT
JLPT N3 grammar · Chapter 16

～のことだから

Predict what someone will do from what you know about them

You’ll be able to use a person’s familiar character or habits as the basis for an expectation or judgment, rather than simply giving a factual reason.

Illustration of the scene described by Knowing grandfather and how early he rises, he has surely already left for his morning walk.
Read it first

早起はやおきな祖父そふのことだから、もう朝あさの散歩さんぽに出でかけたはずです。

hayaoki na sofu no koto da kara, mou asa no sanpo ni dekaketa hazu desu.

What do you think this sentence means?

Knowing grandfather and how early he rises, he has surely already left for his morning walk.

Why it means that

Predict behavior based on a person's character

～のことだから attaches to a person's name or reference to predict what they will do based on their known personality, habits, or characteristic behavior ("knowing them, they will surely...").

Examples

彼女かのじょのことだから、また遅おくれて来くるだろう。

kanojo no koto da kara, mata okurete kuru darou.

Knowing her, she’ll probably be late again.

優やさしい兄あにのことだから、きっと手伝てつだってくれるよ。

yasashii ani no koto da kara, kitto tetsudatte kureru yo.

Knowing how kind my older brother is, he’ll surely help.

How it is built

Attach のことだから to a person

Attach のことだから to a noun referring to a person whose character is well known. The sentence usually finishes with a prediction such as だろう, はずだ, or に違ちがいない.

noun (person)+ のことだから
Example

料理りょうりが上手じょうずな母ははのことだから、おいしい夕飯ゆうはんを用意よういしているはずだ。

ryouri ga jouzu na haha no koto da kara, oishii yuuhan o youi shite iru hazu da.

Knowing my mother who is good at cooking, she is sure to have prepared a delicious dinner.

Examples

時間じかんに厳きびしい部長ぶちょうのことだから、会議かいぎは九時くじちょうどに始はじまるだろう。

jikan ni kibishii buchou no koto dakara, kaigi wa kuji choudo ni hajimaru darou.

Knowing our department manager, who is strict about time, the meeting will probably start at exactly nine.

新あたらしいものが好すきな父ちちのことだから、新あたらしいスマホが出でたらすぐに買かうに違ちがいない。

atarashii mono ga suki na chichi no koto dakara, atarashii sumaho ga detara sugu ni kau ni chigai nai.

Knowing my dad, who loves new things, he’s sure to buy the new smartphone as soon as it comes out.

甘あまいものが大好だいすきな妹いもうとのことだから、お土産みやげのケーキをきっと喜よろこぶよ。

amai mono ga daisuki na imouto no koto dakara, omiyage no keeki o kitto yorokobu yo.

Knowing my little sister, who loves sweets, she’s sure to be happy with the cake we’re bringing.

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