Colonel (abbreviated as Col., Col or COL) is a senior military officer rank used in many countries. It is also used in some police forces and paramilitary organizations.
In the 17th, 18th and 19th centuries, a colonel was typically in charge of a regiment in an army. Modern usage varies greatly, and in some cases, the term is used as an honorific title that may have no direct relationship to military service. The rank of colonel is typically above the rank of lieutenant colonel. The rank above colonel is typically called brigadier, brigade general or brigadier general. In some smaller military forces, such as those of Monaco or the Vatican, colonel is the highest rank.
Equivalent naval ranks may be called captain or ship-of-the-line captain. In the Commonwealth's air force ranking system, the equivalent rank is group captain.
By the end of the late medieval period, a group of "companies" was referred to as a "column" of an army. According to Raymond Oliver, around 1500, the Spanish began explicitly reorganizing part of their army into 20 colunelas or columns of approximately 1000–1250 soldiers. Each colunela was commanded by a cabo de colunela or column head. Because they were crown units, the units were also confusingly called coronelas, and their commanders coronels. Evidence of this can be seen when Gonzalo Fernández de Córdoba, nicknamed "the Great Captain", divided his armies in coronelías, each led by a coronel (colonel), in 1508.
Later, in the 16th century, the French army adopted this organizational structure, renaming colunelas regiments. Even so, they simply Gallicized colunela to the French colonel and pronounced it as written. The English then copied the unit and rank from the French. However, for reasons unknown, the English adopted the Spanish pronunciation of coronel, and after several decades of use shortened it to its current two-syllable pronuciation "kernel". Colonel is linked to the word column (from Latin: columna; Italian: colonna; French: colonne) in a similar way that brigadier is linked to brigade, although in English this relationship is not immediately obvious.