Military rank
Typical army and marine field officer ranks include colonel, lieutenant colonel, major and, in the British army, captains holding an adjutant's or operations officer appointment. In many Commonwealth countries the field rank of brigadier is used, although it fills the position held by brigadier general in other countries. In the United States Army, warrant officers who hold the rank of CW3–CW4 are field grade officers; CW5s are senior field grade officers.
Naval and coast guard senior officer ranks include captain and commander. In some countries, the more senior rank of commodore is also included. In others lieutenant commanders, as equivalents to army and marine majors, are considered senior officers.
Commonwealth air force senior officer ranks include group captain, wing commander, and squadron leader, where such ranks are still used.

Company grade or junior officers: The ranks of junior officers are the three or four lowest ranks of officers. Units under their command are generally not expected to operate independently for any significant length of time. Company grade officers also fill staff roles in some units. In some militaries, however, a captain may act as the permanent commanding officer of an independent company-sized army unit, for example a signal or field engineer squadron, or a field artillery battery.
Typical army company officer ranks include captain and various grades of lieutenant. Typical naval and coast guard junior officer ranks include grades of lieutenant commander, lieutenant, lieutenant junior grade, sub-lieutenant and ensign. Commonwealth (excluding Canada) air force junior officer ranks usually include flight lieutenant, flying officer, and pilot officer.

Subordinate or student officer: Officers in training in the Canadian Armed Forces are either naval cadet for naval training or officer cadet for army or air force training.
In the US and several other western forces, officers in training are referred to as student officers, and carry the rank of cadet (army and air force) or midshipman (navy, and in some countries, marines). These officers may be serving at a military academy, or, as common in the United States, as members of a military training unit attached to a civilian college or university, such as an ROTC unit. This is due to a requirement that commissioned officers have at least a four-year collegiate undergraduate degree.
The British Army refers to its trainee officers as officer cadets, who rank as private soldiers at the start of their training, with no authority over other ranks (except when appointed to carry out a role as part of training). Officer cadets are addressed to as "Mister" or "Miss" until the completion of the early stages of their training at the Royal Military Academy Sandhurst (at which point cadets "pass out" and formally gain their commissions), thereafter other ranks (non-officers) will address them as "Sir" or "Ma'am".
While cadet has always been a rank of limited authority and prestige (cadets and US Navy midshipmen have no authority over commissioned personnel, warrants, or officers, only subordinate cadets), midshipman has historically been a rank with limited leadership responsibility, particularly in the Royal Navy (where cadets are commissioned at the start of their training, unlike their army counterparts). This tradition was continued by the US Navy after its original adoption of the rank, but now US Navy midshipmen are limited in the same manner as cadets in the other US services. Additionally, US Marine officers in training are also midshipmen, trained and educated alongside their naval counterparts, and wear distinctive insignia to indicate their branch of service.
US Coast Guard Academy students are referred to as "cadets", while those attending the military branch's officer candidate school are "officer candidates".
In the US an alternative to spending four years as a cadet or midshipmen is for college graduates with a four-year degree to attend officer candidate school, an intensive twelve-week training course designed to convert college graduates into military officers. Each service has at least one, and usually several, officer candidate school facilities. Students at these programs are called officer candidates.

Warrant officers: Warrant officers (as receiving authority by virtue of a warrant) are a hybrid rank treated slightly differently in each country or service. Warrant officers may either be effectively senior non-commissioned officers or an entirely separate grade between commissioned and non-commissioned officers, usually held by specialist personnel.
In the United States, warrant officers are appointed by warrant then commissioned by the President of the United States at the rank of chief warrant officer. Warrant officers range from WO1–CW5. A warrant officer is not a chief warrant officer until they reach W2. CW3–CW4 are field grade officers. Warrant officers in the rank or grade of CW5 are senior field grade officers.

Enlisted personnel: Enlisted personnel are personnel below commissioned rank and make up the vast majority of military personnel. They are known by different names in different countries, such as other ranks (ORs) in the United Kingdom and some Commonwealth countries, and non-commissioned members (NCMs) in Canada.

Non-commissioned officers: Non-commissioned officers (NCOs) are enlisted personnel, under the command of an officer, granted delegated authority to supervise other military members or assigned significant administrative responsibilities. They are responsible for the care and direct control of junior military members, often functioning in the smaller field units as executive officers.
Even the most senior NCO officially ranks beneath the most junior commissioned officer or warrant officer. However, most senior NCOs have more experience, possibly including combat, than junior officers. In many armies, because junior officers have a great amount of responsibility and authority but little operational experience, they are paired with senior NCO advisers. In some organizations, senior NCOs may have formal responsibility and informal respect beyond that of junior officers, but less than that of warrant officers. Many warrant officers come from the ranks of mid-career NCOs. In some countries warrant ranks replace senior enlisted ranks.
NCO ranks typically include a varying number of grades of sergeant and corporal (air force, army and marines), or chief petty officer and petty officer (navy and coast guard). In many navies the term 'rating' is used to designate specialty, while rank denotes pay grade.
In some countries warrant officers come under the non-commissioned officer branch (senior non-commissioned officiers).

Other enlisted: Personnel with no command authority usually bear titles such as private, airman or aircraftman, or seaman (starting with seaman recruit in the United States Navy and Coast Guard). In the United States Marine Corps individuals of all ranks regardless of command status may be referred to as "marine". In the United States Air Force individuals of all ranks regardless of command status may be referred to as "airman". Shortly after the Sailor's Creed was formally instituted, Secretary of the Navy John Dalton directed that the word sailor should be capitalized when referring to any uniformed member of the Navy. In some countries and services, personnel in different branches have different titles. These may have a variety of grades, such as private first class, but these usually only reflect variations in pay, not increased authority. These may or may not technically be ranks, depending on the country or service. Each rank gives the individual an indication of how long and how well they have served in combat and training.

Appointment: Appointment is the instrument by virtue of which the person exercises their authority. Officers are appointed by a royal commission in most monarchies or a presidential commission in many other countries. In the Commonwealth, warrant officers hold a royal or presidential warrant. In the United States, officers are appointed by the president, with the advice and consent of the United States Senate. Most officers are approved en bloc by voice vote, but flag officers are usually required to appear before the Armed Services Committee and answer questions to the satisfaction of its members, prior to a vote on their commission.
NCOs are appointed by an instrument of appointment, a written document, often a certificate, usually from the service head. Entry into service is often referred to as enlistment throughout the English-speaking world, even in countries where soldiers do not technically enlist.
Sometimes personnel serve in an appointment which is higher than their actual rank. For instance, commodore used to be an appointment of captain in the Royal Navy and lance corporal used to be an appointment of private in the British Army.

Types of rank: There are a number of different forms of rank; from highest to lowest degree, they are:

Substantive or permanent: the fully paid and confirmed rank, with eligibility for the corresponding pension and benefits
Retired or retained: usually granted to those officers of the rank of lieutenant in the navy, or captain in the army, or above, and enlisted, who have reached the end of their service obligation and have not been dishonorably discharged or dismissed from the service. A retired rank is usually kept for life, if the officer concerned so wishes. In the Commonwealth of Nations, such an officer will also hold the style of Esquire, if they do not hold a higher title. In the United Kingdom, an officer of the regular service placed on the retired list or on the reserve will be shown in his/her substantive rank. An officer of the rank of lieutenant, captain, flight lieutenant or above leaving the reserve, or having no reserve liability is permitted to use their rank a courtesy title if they have completed 3 years service in the active list.
Veterans rank is different in each country. Members of the United States military maintain their highest rank after discharge or retirement. 10 U.S.