A subject-matter expert (SME) or domain expert is a person who is an authority in a particular area or topic. The term domain expert is frequently used in expert systems software development, and there the term always refers to the domain other than the software domain. A domain expert is a person with special knowledge or skills in a particular area of endeavour. (An accountant is an expert in the domain of accountancy, for example.) The development of accounting software requires knowledge in two different domains: accounting and software. Some of the development workers may be experts in one domain and not the other. A SME should also have basic knowledge of other technical subjects.
In general, the term is used when developing materials (a book, an examination, a manual, etc.) about a topic, and expertise on the topic is needed by the personnel developing the material. For example, tests are often created by a team of psychometricians and a team of subject-matter experts. The psychometricians understand how to engineer a test while the subject-matter experts understand the actual content of the exam. Books, manuals, and technical documentation are developed by technical writers and instructional designers in conjunctions with SMEs. Technical communicators interview SMEs to extract information and convert it into a form suitable for the audience. SMEs are often required to sign off on the documents or training developed, checking it for technical accuracy. SMEs are also necessary for the development of training materials.
In software engineering environments, the term is used to describe professionals with expertise in the field of application. The term SME also has a broader definition in engineering and high tech as one who has the greatest expertise in a technical topic. SMEs are often asked to review, improve, and approve technical work; to guide others; and to teach. According to Six Sigma, a subject-matter expert "exhibits the highest level of expertise in performing a specialized job, task, or skill of broad definition."