In a frenetic manner; with wild, uncontrolled energy and intensity.
The adverb form of frenetic, created by adding the adverbial suffix -ly to the adjective, following standard English word formation patterns that date back to Old English.
The -ly suffix is one of English's most powerful tools—it turns almost any adjective into an adverb describing how something happens, which is why you'll see it on hundreds of words from ancient roots like this one.
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