Beauteously means “in a beautiful way.” It is the adverb from the old, rather grand adjective beauteous, which already means beautiful. Though actually almost nobody says beauteously in ordinary talk. You meet it in poems, hymns, and old-fashioned stories, where a writer wants the line to sound fine and a little antique. The living everyday word is beautifully. If a friend described a sunset as beauteous, you would hear the extra polish: not just “nice to look at,” but “beautiful” said with a lifted chin. The -ly does the usual job: it turns that feeling into a way of doing or appearing. Use it when you are reading literature and want to keep the old music of the sentence. In class, in a shop, or in a message to a friend, beautifully will sound natural; beauteously will sound as if you have stepped out of a book — which is not wrong, only rare, and a little theatrical.

美麗地（文雅、偏古；口語一般說 beautifully）