The words that open a question in Arabic.
Like English, these sit at the very start of the question.
كَيْفَ vs أَنَّىٰ — كَيْفَ asks plainly how or in what state; أَنَّىٰ adds wonder or improbability, and can also mean "from where". مَتَىٰ vs أَيَّانَ — مَتَىٰ is the general "when"; أَيَّانَ is emphatic, reserved for momentous events like the Hour.