In the field of book publishing, a collection, or more precisely editorial collection (French: collection éditoriale; Spanish: colección editorial; Italian: collana editoriale; Portuguese: coleção de livros, lit. 'collection of books') is a set of books published by the same publisher, usually written by various authors, grouped under the same title, each book with a particular title. The collective title is the title of the collection, it must be mentioned on each book.
The books that make up an editorial collection can be published in a specific order or not. When each volume in the collection has a serial number, it is called a numbered collection.
A collection generally using distinctive, common formats and features. The title of a collection can be accompanied by the term "series" or its equivalents in other languages, such as in the English-speaking world, for example, the Bibliothèque de la Pléiade, Découvertes Gallimard and Que sais-je ? are all termed book series instead of collections.