OF-3

Common military ranks in English
Navies	Armies	Air forces
Commissioned and Non-commissioned officers
Admiral of the fleet	Marshal or Field marshal	Marshal of the air force
Admiral	General	Air chief marshal
Vice admiral	Lieutenant general	Air marshal
Rear admiral	Major general	Air vice-marshal
Commodore	Brigadier or Brigadier general	Air commodore
Captain	Colonel	Group captain
Commander	Lieutenant colonel	Wing commander
Lieutenant commander	Major or Commandant	Squadron leader
Lieutenant	Captain	Flight lieutenant
Sub-lieutenant	Lieutenant or First lieutenant	Flying officer
Ensign	Second lieutenant	Pilot officer
Midshipman	Officer cadet	Flight cadet
Enlisted grades
Warrant officer or Chief petty officer	Warrant officer or Sergeant major	Warrant officer
Petty officer	Sergeant	Sergeant
Leading seaman	Corporal	Corporal
Seaman	Private	Aircraftman

Ranks and insignia of NATO are combined military insignia used by the member countries of the North Atlantic Treaty Organization.

The rank scale is used for specifying posts within NATO.

NATO maintains a "standard rank scale" in an attempt to match every member country's military rank to corresponding ranks used by the other members. The rank categories were established in the document STANAG 2116, formally titled NATO Codes for Grades of Military Personnel. There are two scales, though not all member countries use all the points on the NATO scales and some have more than one rank at some points (e.g. many forces have two ranks at OF-1, usually lieutenants):

The numbers in the system broadly correspond to the US military pay grade system, with OR-x replacing E-x and WO-x replacing W-x. The main difference is in the commissioned officer ranks, where the US system recognises two ranks at OF-1 level (O-1 and O-2), meaning that all O-x numbers after O-1 are one point higher on the US scale than they are on the NATO scale (e.g. a major is OF-3 on the NATO scale and O-4 on the US scale).

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Wikipedia