Regiment
A regiment is a military unit. Their role and size varies markedly, depending on the country and the arm of service.
In Medieval Europe, the term "regiment" denoted any large body of front-line soldiers, recruited or conscripted in one geographical area, by a leader who was often also the feudal lord of the soldiers.
By the 17th Century, a full-strength regiment was usually about a thousand personnel, and was usually commanded by a colonel.
Definitions
During the modern era, the word "regiment" – much like "corps" – may have two somewhat divergent meanings, which refer to two distinct roles:
a front-line military formation, and/or;
an administrative and/or ceremonial unit.
In many armies, the first role, of front-line unit, has been assumed by independent battalions, battlegroups, task forces, brigades and/or other, similarly-sized operational units. However, these non-regimental units tend to be short-lived, and regiments, have tended to retain their traditional responsibilities for: ceremonial duties, the recruitment of volunteers, induction of new recruits, morale/esprit de corps and administrative roles (such as pay).