What is the difference between "開く", "空く", "打ち解ける", "うちとける", "散開星団"?

"開く" means "to open (intransitive)", "空く" means "to open, to be vacant, to be available, to become empty", "打ち解ける" means "to open one's heart, to become friendly, to relax", "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".

Quintuple VS

Synonym Boundary: "開く", "空く", "打ち解ける", "うちとける", "散開星団"

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

打ち解ける

うちとける (uchitokeru)

N2 / CEFR

Japanese Option D

うちとける

うちとける (uchitokeru)

N2 / CEFR

Japanese Option E

散開星団

さんかいせいだん (sankaiseidan)

C2 / CEFR

Quintuple VS Nuance Contrast & Social Differences

When expressing "open" in Japanese, you must carefully distinguish between "開く", "空く", "打ち解ける", "うちとける", "散開星団" 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.
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」..
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..

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 "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 "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.

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.".