Subtle describes something that is delicate, hard to notice, or not obvious, often requiring careful attention to understand or appreciate.
From Old French 'sotil', from Latin 'subtilis' meaning 'fine, thin, delicate', literally 'woven under' or 'finely spun'. It referred to things so finely made or thought out that they were hard to see clearly.
The silent 'b' in 'subtle' is itself subtle—a quiet reminder of its Latin past. Subtle things are powerful precisely because they slip under your radar: a tiny change in tone, a hint of flavor, or a barely noticeable shift in mood.
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