How and what are used in exclamations, how with anAdjective or Adverb alone, what with anAdjective and a Noun or a Noun alone, e.g.:
(Adjective)
How strange!
(Que estrany!)(Adverb)
How fast they talk!(Que ràpid que parlen!)
(Singular Countable Noun)
What a strange coincidence!
('Quina coincidència tan rara!)
(Plural Countable Noun)
What wonderful flowers!
(Quines flors tan meravelloses!)
(Singular Countable Noun)
What an idiot!
(Quin imbècil!)
(Uncountable Noun)
What nonsense!
(Quin galimaties!)