Consultant

A consultant (from the Latin consultare means "to discuss" from which we also derive words such as consul and counsel) is a professional who provides advice in a particular area of expertise such as management, accountancy, the environment, entertainment, technology, law (tax law, in particular), human resources, marketing, emergency management, food production, medicine, finance, life management, economics, public affairs, communication, engineering, sound system design, graphic design, or waste management.
A consultant is usually an expert or a professional in a specific field and has a wide knowledge of the subject matter. A consultant usually works for a consultancy firm or is self-employed, and engages with multiple and changing clients. Thus, clients have access to deeper levels of expertise than would be feasible for them to retain in-house, and may purchase only as much service from the outside consultant as desired.
'Consultant' is also the term used to denote the most senior medical position in the United Kingdom, Australia and Ireland (e.g., a consultant surgeon).

[edit] Ways in which consultants work

Some consultants are employed by a consult staffing company, a company that provides consultants to clients. This is particularly common in the technology sector. Consultants are often called contractors in the technology sector in reference to their employment contract.
Strategy consultants are common in upper management in many industries. There are also independent consultants who act as interim executives with decision-making power under corporate policies or statutes. They may sit on specially constituted boards or committees.
Consultants work at client places on behalf of a consultancy or Billing company.