1. "brand-new" is an adjective that can serve as an attributive, suffixed to a noun, for example, "a brand-new book."2. "brandnew" is not necessarily an adjective and may not be used as an attributive. It implies newness but may not be followed by a noun.3. "Brand" is a noun that can act as an adjective. For instance, "sunglasses" is a noun that functions as an adjective.4. While "brand" has an adverbial sense, it is not applicable in this phrase, which is a combination of "brand" and "new" functioning as an adjective phrase.5. The phrase can be written as "brand-new," with a hyphen, or as "brandnew," without a hyphen, but the meaning remains the same, indicating something that is completely new.
