In a way that is light, airy, delicate, or heavenly; with a quality of being spiritual rather than physical.
From ethereal plus -ly (adverb suffix). The -ly ending transforms adjectives into adverbs showing manner or quality.
Adding -ly to create adverbs is one of the most productive word-formation patterns in English — it's so automatic that English speakers instantly understand new adverbs even if they've never heard them before, like 'zoomily' or 'unicornly.'
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