Consultant (noun)

1. A person who is an expert in a particular field and who works for an organization providing advice and expertise.
2. An expert who advises companies or other organizations.

Origin:

Mid 18th century: from consult, on the pattern of agent.

Examples:

1. She hired a consultant to help with the project.
2. He is a consultant in the field of marketing.
3. The company has several consultants working on the project.
4. The consultant provided valuable advice.
5. She is a consultant for several companies.