毫无 (háo wú) means 'not in the least' or 'to completely lack' and is always followed by a noun (e.g., 毫无兴趣 'no interest at all'). Its near-synonym 毫不 (háo bù) is used before an adjective or verb (e.g., 毫不关心 'not care at all'), so the choice depends on what part of speech follows.