What is the difference between "開く", "開通する", "うちとける", "散開星団", "公開市場操作"?

"開く" means "to open (intransitive)", "開通する" means "to open (for traffic), to be completed (e.g., a tunnel, bridge, line)", "うちとける" means "to open one's heart, to feel at home, to relax, to be frank", "散開星団" means "Open cluster", "公開市場操作" means "Open Market Operations".

Quintuple VS

Synonym Boundary: "開く", "開通する", "うちとける", "散開星団", "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

開通する

かいつうする (kaitsū suru)

N3 / CEFR

Japanese Option C

うちとける

うちとける (uchitokeru)

N2 / CEFR

Japanese Option D

散開星団

さんかいせいだん (sankaiseidan)

C2 / 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", "開通する", "うちとける", "散開星団", "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.
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..
うちとける (うちとける (uchitokeru) - Level: N2): Maps to "to open one's heart, to feel at home, to relax, to be frank" and is used when Describes the process of becoming comfortable and relaxed with someone, allowing one's true self to show. Often implies breaking down barriers. 心を開き、親しくなる様子を表します。.
散開星団 (さんかいせいだん (sankaiseidan) - Level: C2): Maps to "Open cluster" and is used when Essential structural term in CEFR C2 vocabulary syllabus..
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 "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 "うちとける"

初めて会った人ともすぐにうちとけることができる。

I can quickly feel at ease even with people I meet for the first time.

Context for "散開星団"

私は散開星団に興味があります。

I am interested in Open cluster.

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.".