is an adverb that is used to convey a ‘considerable’ amount of something. It is often translated as ‘quite’, ‘fairly’, ‘considerably’, or ‘pretty’. かなり
will almost always appear directly before a phrase, or directly before a noun (in which case の will come between the noun and かなり).
This month we used a considerable amount of money again, didn't we?
Because I was working all day today, I am pretty tired.
Since there is a considerable distance to Mexico, you will get there quicker if you go by airplane, rather than by boat.
Quite a lot of people got hurt in the accident today.
originally came from 可也（かなり）, and more recently 可成（かなり）. Both of these expressions mean something similar to ‘to become undeniable’, with the former structure using an older kanji for ‘to become’ 也（なり）. かなり
is still used this way today, highlighting that the amount/existence of something has reached a point that cannot be denied. かなり
may be seen with this meaning when carrying either positive and negative connotations.
You made it for the first time? It's pretty good!
It's quite painful. Do you think a bone is broken?