Is Suddenly an Adjective or Adverb?

SUDDENLY (adverb) definition and synonyms | Macmillan Dictionary.

Is suddenly a adjective?

Happening quickly and with little or no warning; in a sudden manner.

Is sudden an adjective and adverb?

As detailed above, 'sudden' can be an adjective or an adverb. Adjective usage: The sudden drop in temperature left everyone cold and confused.