The English term comics is used as a singular noun when it refers to the medium and a plural when referring to particular instances, such as individual strips or comic books. Though the term derives from the humorous (or comic) work that predominated in early American newspaper comic strips, it has become standard also for non-humorous works. It is common in English to refer to the comics of different cultures by the terms used in their original languages, such as manga for Japanese comics, or bandes dessinées for French-language comics. There is no consensus amongst theorists and historians on a definition of comics; some emphasize the combination of images and text, some sequentiality or other image relations, and others historical aspects such as mass reproduction or the use of recurring characters. The increasing cross-pollination of concepts from different comics cultures and eras has further made definition difficult.