Faculty (in North American usage) or academics (in British usage) are the academic staff of a university: professors of various ranks, lecturers, and/or researchers. The term faculty in this sense is most commonly used in this context in the United States and Canada, and generally includes professors of various ranks: adjunct professors, assistant professors, associate professors, and (full) professors, usually tenured (or tenure-track) in terms of their contract of employment. In British English "faculty" usually refers to a university's department, not to the employees.
Members of university administration (e.g., department chairs, deans, vice presidents, presidents, and librarians) are often also faculty members, in many cases beginning (and remaining) as professors. In some universities, the distinction between 'academic faculty' and 'administrative faculty' is made explicit by the former being contracted for nine months per year, meaning that they can devote their time to research (and possibly be absent from the campus) during the summer months, while the latter are contracted for twelve months per year. These two types of faculty status are sometimes known as 'nine-month faculty' and 'twelve-month faculty'. Faculty who are paid a nine-month salary are typically allowed to seek external funds from grant agencies to partially or fully support their research activities during the summer months.
Most university faculty members hold a Ph.D. or equivalent doctorate degree. Some professionals or instructors from other institutions who are associated with a particular university (e.g., by teaching some courses or supervising graduate students) but do not hold professorships may be appointed as adjunct faculty.