Any holder of an office or of a post may bear the title officer. Generally, the word officer implies a rank, and degree of decision-making responsibility, higher rather than lower in a chain of command and reporting.

However, in some organizations that use the term, all but clerical workers are termed officers (in the U.S., police departments and the diplomatic service).

In military service, non-commissioned officer (NCO) (or petty officer in naval service) is a usually lower ranking officer with less responsibility (some sergeant majors, or sergeants major, are an exceptions with respect to both rank and responsibility) than any commissioned officer; their careers are also subject to different rules from those with commissions.

Examples include:

• Ship's officer - a senior member of a ship's company, such as a captain.
• Customs officer - An American inspector of imported goods.
• Revenue officer - A UK inspector of imported goods.
• Political officer - Position that answers to a separate chain of command controlled by a Communist Party. Compare commissar.
• Chief Academic Officer - Position in charge of instructional and research affairs.
• Company officer - an employee of a company who is delegated various rights as an agent of the company.
  • Chief executive officer - The ranking manager who heads all the other officers of a company.
  • Chief financial officer - The head of a group of financial officers .
  • Chief information officer - The head of a group of information officers .
  • Chief operations officer
• Commissioned officer - Member of a military or paramilitary force who is commissioned by the government. Compare military rank.
• Non-commissioned officer - in the military hierarchy, a junior-ranked, non-sworn executive buffer between commissioned officers and military enlistees.
• Police officer - non-military government employee charged with upholding the law; in the U.S., distinguished from civilians as a sworn officer . In England and Wales; a citizen locally appointed by the Crown and not a governmental employee.

Officer is also a suburb of Melbourne, Australia.