Now, we can turn any adjective into an adverb in Japanese very easily. All we do is we take the regular い ending adjective and use its stem く.
So 早い becomes 早く. 早い is an adjective describing a thing; 早く is an adverb describing an action. So: ウサギは早く走って...
But 「急に」what does that mean? Well, 急 is a noun and it means sudden.
And when we put に onto the end of it we turn that into an adverb as well. So here we have two kinds of adverbs. We can form an adverb from an adjective by simply using its く-stem. And we form an adverb from a noun by adding に.
