Regiment

Regiment is a large group of soldiers [Cambridge Dictionary].
A regiment, in most armies, is a body of troops headed by a colonel and organized for tactical control into companies, battalions, or squadrons. French cavalry units were called regiments as early as 1558. The word is derived from the Latin regimen, a rule or system of order, and describes the regiment’s functions of raising, equipping, and training troops. As a regiment acquired individuality, colors, coat of arms, distinctive uniform and insignia, and achievements in battle, it also became a central object of loyalty, pride, and esprit de corps of its soldiers [Britannica].

Sources:

Regiment. Cambridge Dictionary. Retrieved from: https://dictionary.cambridge.org/dictionary/english/regiment

Regiment. Britannica. Retrieved from: https://www.britannica.com/topic/regiment