In British English the hyphen is standard (north-west); American English often writes it as one word (northwest). The adverb form describes where something is located or which way something moves.
常見錯誤
We travelled to north-west
We travelled north-west
north-west as an adverb does not need a preposition like 'to' before it.
The north-west wind' (when meaning wind direction)
The north-westerly wind' or 'The wind blew from the north-west
as an adverb, north-west describes movement direction, not the source of the wind.