空
クウ, そら, あ.く, あ.き, あ.ける, から, す.く, す.かす, むな.しい, うつ, き, く

empty, sky, void, vacant, vacuum

JLPT4 G1 S8 F304

As per 工# (connecting pipe/tube) + 穴 hole → *empty* *space* inside a connecting pipe/tube → *vacant* → *sky*; *the air*; → *absent-minded*; *pretend* (← no substance).

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