vastly 極大地 - Very great in size

vastly 極大地 - Very great in size

1. Very great in size, extent, or quantity. See Synonyms at enormous.
2. Very great in scope or import: a vast improvement.

The two languages are vastly different in many important ways. "JavaScript" is as related to "Java" as "Carnival" is to "Car".

Reference:

https://github.com/getify/You-Dont-Know-JS/blob/master/preface.md