温 = 'warm / mild', 婉 = 'graceful / tactful'. Per 《新华词典》: 温和柔顺 — 'mild and yielding'. Almost exclusively used about women (as a traditional compliment) or about voices/melodies. Contrast with 泼辣 (feisty) or 强势 (forceful).
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Somewhat literary. More common in novels, romance dramas, and character descriptions than in casual speech, where 温柔 (gentle) is the everyday equivalent.
