Newspapers, as one of the most popular mass media forms in modern information society, perform four basic functions: information, entertainment, persuasion, and the transmission of culture. These can easily be accompanied by their educational, psychotherapeutic, and integrative functions. That is why newspapers are often given the meaning of a specific public service. Despite the fact that newspapers are very difficult to define, many theoreticians of journalism have debated what the newspapers really are. Their opinions correspond in many aspects, but even today there are so many definitions and variations on certain newspaper features that it is almost impossible to achieve a consensus. Among many newspaper definitions we point out the one given by Eric W. Allen in 1930, which has been referred to by a number of later scholars. Among more recent ones are the definitions by Kunczik Michael and Astrid Zipfel given in 2006. Since newspapers have many functions in social communities they represent important material and source of information for libraries, museums, and archives. That is why they find the question of defining newspapers important, too. In library circles the generally accepted definition of newspapers today is the one given in ISBD(CR): International Standard Bibliographic Description for Serials and Other Continuing Resources.