With speed; in a rapid manner.
"The snow melted rapidly after the warm sun broke through the clouds."
In plain English: Rapidly means happening very quickly.
"The snow melted rapidly after the sun came out."
Usage: Use rapidly to describe how quickly an action happens, such as prices rising or snow melting fast. It is often confused with the adjective "rapid," which modifies nouns like a "rapid river."
The word rapidly is formed by adding the suffix -ly to the adjective rapid. It entered English as a straightforward modification of an existing term rather than through borrowing from another language.