A co-author is an author who works together with one or several other authors to produce a text. This term has different nuances of meaning in various fields of writing. In fiction if generally refers to one of only two or, perhaps, three authors who collaborate on a book. On the other hand, in the realm of non-fiction, a co-author may also be a subordinate technical specialist brought in to perform technical writing tasks in the preparation of a manuscript. Scientific writing uses the term much more broadly, and co-authorship has a special and particular role in the publication of academic and scientific work.
Fiction writing is often the province of lone wolf writers who work by themselves, although they often chat with groups of friends and colleagues who offer input on a work in progress. Some fiction authors prefer to work together on projects, however. An author may simply be more comfortable writing literature as a team, and the world of fiction includes examples of husband and wife writing teams as well as pairs or trios of co-authors who are simply good friends. In other cases, authors who primarily work alone may opt to work on a collaborative project when they suspect that it will yield a particularly interesting product.
In the realm of non-fiction, these same types of co-author partnerships exist as well. Other works of non-fiction, especially those written by major cultural or political figures who have interesting stories to tell but either limited time or insufficient skill at writing, may use co-authors to make up for those deficiencies. In such cases, a co-author may be brought onto a project as a junior partner and does not generate the content of books, but, instead, shapes the language.
Co-authorship plays a different role in the sciences than it does in the realm of fiction, as scientific projects are often the result of work done by a large team of investigators. The convention in most scientific fields is to acknowledge the work of all of the researchers who made significant contributions to a study by listing them as co-authors. In theory, all the authors of a scientific study should agree on the conclusions presented in a finished paper, although in practice, this level of consensus can be difficult to achieve, especially when larger research teams are involved.
All varieties of co-authorship require a high level of cooperation in order to be successful. An ideal co-author does more than simply share the work of a project. Whether in science or fiction, members of successful writing teams will encourage, inspire and motivate one another.