more rapidly
more rapidly, most rapidly
A superlative form of something compares three or more things. For example, the superlative form of beautiful would be most beautiful and the comparative form would be more beautiful. Another example would be big, superlative would be biggest and comparative would be bigger.
The comparative adverb form for "rapid" is "more rapidly." In English, adverbs that do not follow the typical -er ending often use "more" to form the comparative. Therefore, when comparing actions or qualities related to speed, one would say "He runs more rapidly than she does."
more rapidly
more rapidly
More quickly would be the comparative form. Any adverb that ends with an "-ly" would take more for comparative and most for the superlative forms.
more rapidly
more rapidly
more rapidly and most rapidly
The comparative form of busy is busier.
The comparative form of dreamy is dreamier
The comparative form of friendly is friendlier.