Hi, Julia! :) Sure, the writer can say what they think they've written, but once an agent or (especially) a publisher is involved, things can change. I know one author who recently submitted what she thought of as a linked story collection to her publisher, who thought it would sell better if marketed as a novel; the author was surprised to hear she'd written a novel, but she agreed to the plan because she trusts her publisher's knowledge of the market. Similarly, with titles, the author generally has input on the final decision, but publishers tend to think of a book's title primarily as a marketing tool. Same with covers—an author's contract might empower them to offer feedback or even to nix a proposed cover design, but ultimately, the cover exists to sell the book, and that's (hopefully!) the publisher's area of expertise.
Is it ever possible that the writer could choose the category of his/her work? Like entering a contest?
Hi, Julia! :) Sure, the writer can say what they think they've written, but once an agent or (especially) a publisher is involved, things can change. I know one author who recently submitted what she thought of as a linked story collection to her publisher, who thought it would sell better if marketed as a novel; the author was surprised to hear she'd written a novel, but she agreed to the plan because she trusts her publisher's knowledge of the market. Similarly, with titles, the author generally has input on the final decision, but publishers tend to think of a book's title primarily as a marketing tool. Same with covers—an author's contract might empower them to offer feedback or even to nix a proposed cover design, but ultimately, the cover exists to sell the book, and that's (hopefully!) the publisher's area of expertise.