Contributor
Also called: other contributors, editor, translator
Anyone credited for a source other than its primary author: editor, translator, illustrator, director, host, or narrator.
Contributors carry role labels because the role changes the citation's meaning. “Ed.” tells the reader the named person assembled the volume rather than wrote it; “Trans.” tells them the words you quoted are the translator's choices.
Which contributors to name depends on what you are citing and why. A chapter citation names the book's editors. A translated novel names the translator — and if your argument is about the translation, the translator may belong in the author position. A film citation names the director in most styles, and MLA lets you lead with whichever contributor your discussion is actually about.