A script doctor, also called a script consultant, is a screenwriter or playwright hired by a film, television or theatre production to rewrite an existing script or polish specific aspects of it, including structure, characterization, dialogue, pacing, theme, and other elements. Under the Writers Guild of America screenwriting credit system, a screenwriter must contribute more than 50 percent of an original screenplay or 33 percent of an adaptation to receive credit. Uncredited screenwriters are not eligible to win the Academy Award for Best Screenplay or the Writers Guild of America Awards.