Whenever you include another person's information or wording in a document, you must acknowledge the source and include a citation that will tell the reader where you obtained it. If you do not do so, you deprive your reader of the ability to locate information that he or she might want to explore further. In addition, you may be committing intellectual theft, plagiarism.
Mechanisms that allow a reader to verify the information presented in a document are essential parts of most types of technical and scientific writing. Procedures sections of technical and laboratory reports, for example, provide the reader with information sufficient to replicate both the method and the data described in the document.
There are two basic and universal rules regarding the use of information in professional and, especially, academic writing:
Using the Language of Your Source Appropriately
Basic Structure and Formats of Citation Styles
American Psychological Association (APA) Author-Date Style
Modern Language Association (MLA) Author-Page Style
Chicago Manual of Style (CMS) Note Citations
Council of Biology Editors (CBE) Citation-Sequence System
IEEE Citation Sequence System