"Rhaid i chi yrru'n araf."
Translation:You must drive slowly.
Does the ' 'n" make araf an adverb? and is this the construction for adverbs generally?
This is one way in which many, but not all, adjectives can be turned into adverbs when they follow a verb, yes, rather as many English adjectives can take a '-ly' ending to become adverbs.
Thanks for the quick reply. There seems to be a lot of new grammar suddenly coming up in this course, and it really helps to understand the sentences in detail, especially when the constructions differ so much from languages I've studied before (English, French, German). Which makes it fascinating, of course!