From Teflpedia

How (/haʊ/) is an English wh-word referring to manner, i.e. ways.[1]

How is the only wh-word that is spelt beginning with an h, though it is not the only one which is pronounced beginning with a /h/ sound, as who, whom, whose (and related words) are too. How used to be written "whow".[2]

How forms lots of how phrases with gradable adjectives and some adverbs.