Unlike many military organizational methods in history, the Mongols firmly believed in a meritocracy to establish the leadership of their forces.
Note: Due to the inconsistancies in the spelling of various terms, I use the ones most convinient for reading.
Unaghan Boghul - Mongol term for serfs.
Arad & Qarachu - Mongol terms for the commoner caste.
Nokud - A military title for the free warrior-retainers of the Mongols. These are the standard soldiers which make up the Mongol Army.
Bahadur - The Mongolian nobility, they were generally organized into elite units of the Imperial Guard, rather than directly into the army and acted as the equivalent to knights.
Yurtchi - The quartermaster of an Ordu, responsible for overseeing many of the daily activities of the army.
Boyan - The general of a Khan, in command of an Ordu, but not related by blood to the Khan.
Orlok - A marshal of an Ordu containing three or more Tumens. This title was generally applied to royal princes related by blood to the Khan.
Ilkhan - This title refers to a provincial Khan who rules as a subordinate to an overall Khan.
Khatun/Khanum - This title is roughly equivalent to queen, and applies to the wife of a Khan.
Khan - While this originally appeared as the title for a tribal leader, it was later equated to king.
Khagan/Great Khan - Essentially translated as "Khan of Khans," equivalent to King of Kings, this title was reserved for the equivalent of the emperor of the Mongolian Empire.
The military organization of the Mongols is a simple, decimal-based scheme.
Arban - The smallest unit, composed to 10 soldiers. Commanded by an Arban-u Darga.
Jagun - A unit of ten Arbans, comprising 100 soldiers. Commanded by a Jagutu-iin Darga.
Mingghan - A unit composed of ten Jagun, comprising 1000 soldiers. COmmanded by a Mingghan-u Noyan.
Tumen - A unit of 10,000 soldiers, composed of ten Mingghan. Commanded by a Tumetu-iin Noyan.
Ordu - The basis for the term "Horde," Ordu were composed of ten to five Tumens, with varying arrangements. One common Ordu composition was three Tumens of light cavalry, with several Minnghans of artillery, commanded by an Orlok. Another standard organization was to use several Tumens of light cavalry horse archers and a couple Tumens of heavy cavalry lancers, arranged in a 60/40 split in favor of light cavalry.