Is Greatly an Adverb or Adjective?

GREATLY (adverb) definition and synonyms | Macmillan Dictionary.

Is the word greatly an adjective?

Nobly; magnanimously. To a great extent or degree. "Expenses greatly exceeded revenues."

What is the adjective form of greatly?

incredibly, largely, tremendously, markedly, mightily, notably, indeed, vastly, highly, extremely, remarkably, enormously, immeasurably, hugely, immensely, abundantly, eminently, emphatically, exceedingly, exceptionally.