What is the difference between "開く", "空く", "開通する", "打ち解ける", "公開市場操作"?

"開く" means "to open (intransitive)", "空く" means "to open, to be vacant, to be available, to become empty", "開通する" means "to open (for traffic), to be completed (e.g., a tunnel, bridge, line)", "打ち解ける" means "to open one's heart, to become friendly, to relax", "公開市場操作" means "Open Market Operations".

Quintuple VS

Synonym Boundary: "開く", "空く", "開通する", "打ち解ける", "公開市場操作"

All represent the core concept "open", but require precise selection.

Japanese Option A

開く

あく (aku)

N4 / CEFR

Japanese Option B

空く

あく (aku)

N4 / CEFR

Japanese Option C

開通する

かいつうする (kaitsū suru)

N3 / CEFR

Japanese Option D

打ち解ける

うちとける (uchitokeru)

N2 / CEFR

Japanese Option E

公開市場操作

こうかいしじょうそうさ (koukaishijousousa)

C2 / CEFR

Quintuple VS Nuance Contrast & Social Differences

When expressing "open" in Japanese, you must carefully distinguish between "開く", "空く", "開通する", "打ち解ける", "公開市場操作" based on context.

開く (あく (aku) - Level: N4): Maps to "to open (intransitive)" and is used when Intransitive verb. Used when something opens on its own or is opened by an unspecified agent.
空く (あく (aku) - Level: N4): Maps to "to open, to be vacant, to be available, to become empty" and is used when An intransitive verb. Refers to something becoming empty, available, or a space opening up. For example, 席が空く.
開通する (かいつうする (kaitsū suru) - Level: N3): Maps to "to open (for traffic), to be completed (e.g., a tunnel, bridge, line)" and is used when Used for infrastructure like roads, railways, tunnels, or new services becoming available for public use. It's an intransitive verb..
打ち解ける (うちとける (uchitokeru) - Level: N2): Maps to "to open one's heart, to become friendly, to relax" and is used when To become less reserved, more relaxed and informal with someone, moving from a formal or tense state to a more comfortable and open one. Often used with the particle 「に」..
公開市場操作 (こうかいしじょうそうさ (koukaishijousousa) - Level: C2): Maps to "Open Market Operations" and is used when Essential structural term in CEFR C2 vocabulary syllabus..

Mixing these up can easily lead to unnatural translations. Refer to the bilingual context cards below to master the boundaries!

Context for "開く"

ドアが自動的に開きます。

The door opens automatically.

Context for "空く"

会議室が空いていますか。

Is the meeting room available?

Context for "開通する"

新しい高速道路が来月開通する予定だ。

The new highway is scheduled to open next month.

Context for "打ち解ける"

彼はどんな人ともすぐに打ち解けることができる。

He can quickly become friendly with anyone.

Context for "公開市場操作"

私は公開市場操作に興味があります。

I am interested in Open Market Operations.

Synonym Mastery Challenge

Which Japanese word perfectly fits this blank space?

Fill in the blank: "ドアが自動的に開きます。" (Meaning: "The door opens automatically.")

🎉 Correct Answer!

Remember: "開く" is correct here because it represents "to open (intransitive)" in the context: "The door opens automatically.".