"his whole attitude had undergone a subtle change" "a subtle difference" "that elusive thing the soul"
"a subtle mind"
"glaucoma is an insidious disease" "a subtle poison"
Many inconsistencies are too subtle for the detection of an ordinary mind.
A change had gradually taken place in Hannah..subtle but unmistakable.
She smiled..that subtle mocking in her eyes.
牛津高階第八版
美國韋氏詞典
Dictionary.com
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維基百科 (自由的百科全書)