JLPT N1Spoken and writtenCritical

をいいことにtaking advantage of

Something convenient is true, such as nobody watching or someone too kind to say no, and a person uses it to do what they shouldn't. It always carries blame, heavy or light.

after a clause

子こどもたちは親おやが見みていないのをいいことに、夜よ中なかまでゲームをしていた。

The children took advantage of their parents not watching and played games into the middle of the night.

after a noun

家や主ぬしの留る守すをいいことに、男おとこは勝かっ手てに部屋へやへ入はいった。

Taking advantage of the landlord's absence, the man let himself into the room.

After a clause

Plain form + の + をいいことに

A noun or a な-adjective takes な: 留る守すなのをいいことに, 新しん人じんなのをいいことに.

After a noun

Noun + をいいことに

留る守すをいいことに.

Before it: An opening: someone is away (留る守す, 出しゅっ張ちょう中ちゅう), nobody is checking (誰だれも見みていない), someone puts up with it (何なにも言いわない, 優やさしい).
After it: What they get away with, often with 勝かっ手てに or 〜放ほう題だい.
Said about: Mostly other people. About yourself it is a guilty admission, usually with てしまった.
Where you'll meet it: Complaints and gossip, and news of misconduct.

In use

上じょう司しが出しゅっ張ちょう中ちゅうなのをいいことに、彼かれは毎まい日にち早はやく帰かえっていた。

He took advantage of his boss being away on a business trip and went home early every day.

彼かの女じょが何なにも言いわないのをいいことに、彼かれは家か事じを全ぜん部ぶ押おしつけている。

Because she never says anything, he gets away with dumping all the housework on her.

妻つまが留る守すなのをいいことに、今こん夜やは一人ひとりでピザを一いち枚まい食たべてしまった。

With my wife out, I took advantage and ate a whole pizza by myself tonight.

About yourself: a guilty admission, not a serious charge.

English "take advantage of" can be innocent

をいいことに never is. When nothing wrong was done, it is を利り用ようして.

Sounds odd: 連れん休きゅうをいいことに、家か族ぞくで京きょう都とへ行いった。

Taking advantage of the long weekend, we went to Kyoto as a family.

It sounds as if the trip were something to feel guilty about. 連れん休きゅうを利り用ようして.

Close neighbours

にかこつけてN1

An excuse, not an opening: an occasion becomes cover for what someone wanted to do anyway.

出しゅっ張ちょうにかこつけて、学がく生せい時じ代だいの友ゆう人じんに会あってきた。

I used the business trip as an excuse to go and see a friend from my student days.

をきっかけにN2

What set a change off. Nothing sly in it.

病びょう気きをきっかけに、彼かれは食しょく生せい活かつを見み直なおした。

His illness prompted him to rethink what he ate.

Check yourself

1What does the writer think of him?

彼かれは先せん輩ぱいが優やさしいのをいいことに、毎まい回かい仕し事ごとを手て伝つだわせている。

Choose an answer to see why.

2Which one fits?

店てん長ちょうが留る守す（　　）、店てん員いんたちはおしゃべりばかりしていた。

Choose an answer to see why.

More detail

Word for word: "treating it as a good thing". Good for them, that is.

More sentences

彼かれは誰だれも帳ちょう簿ぼを確かく認にんしないのをいいことに、売うり上あげの数すう字じを書かき換かえていた。

Taking advantage of the fact that nobody checked the books, he had been altering the sales figures.

警けい備びが手て薄うすなのをいいことに、何なに者ものかが資し材ざいを持もち出だした。

Taking advantage of the thin security, someone made off with the materials.

父ちちの留る守すをいいことに、子こどもたちは居い間まを散ちらかし放ほう題だいにした。

With their father out, the children took advantage and made as much mess as they liked in the living room.

店みせが空すいているのをいいことに、私わたしたちは閉へい店てん近ちかくまで長なが居いしてしまった。

The place was empty, so we took advantage and stayed until nearly closing time.