Most academic and research libraries use the Library of Congress Classification scheme to organize their information. This system divides all knowledge by subject or discipline. The Library of Congress Classification is divided into 21 basic classes and then further divided into subclasses. Often you may be researching a topic that will fall in more than one subject area. For example, if you were researching the topic of Abortion you may find information in the subject areas of law, ethics, social sciences, religion or medicine. In this case, selecting a subject area and your information sources then depends on the approach you decide to take with your research topic.
When conducting scholarly and academic research, the language used in information sources is that of the discipline covered, and typically assumes some subject background knowledge on the part of the reader. Trade information sources are often written in a profession's jargon, in a language that would be familiar to people that work, or are studying to enter into a career in that profession or industry.