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ring finger; third finger; fourth finger (esp. in piano-playing)
fourth toe
結婚指輪は左手の薬指にはめるのが一般的だね。
It's common to wear a wedding ring on the left ring finger.
薬指は他の指より力が入りにくいと言われている。
It's said that the ring finger is harder to put strength into than other fingers.
彼女の薬指にダイヤの指輪が光っていたのが見えた。
I saw a diamond ring shining on her ring finger.