Vastly adv. : To a vast extent or degree; very greatly; immensely.

Example:
Invertebrate circulatory systems are Vastly different than those of vertebrates?

Taxonomy
vastly, WordNet, word meaning, adverb, Translations, German military, Unanswered questions, Português, 中文, Chinese, military leader, extent, Synonym, adjective, Search, Dansk, Danish, stor.

Defination from the web:
vastly has one meaning: Meaning #1 : to an exceedingly great ... vastly. Paul von Lettow-Vorbeck (German military leader) infinitely. transcribbler. Heart (1991 Album by Gary Numan) ...