An artillery unit equivalent to an infantry company. The original meaning (16th century) was the platform or fortified structure on which or withing the artillery was mounted; later it included the guns there mounted; and still later, as mobile artillery became commonplace, it came to mean the guns alone. Subunits are called troops.While artillery batteries are historically the basic tactical unit which can operate independently, infantry companies and cavalry squadrons are rarely separated for long periods from their parent unit (the battalion or regiment). An administrative collection of artillery batteries was called a battalion in the 18th century, a brigade until 1938, and since then a regiment. Tactical artillery regiments all belong to the corps (family) known as The Royal Regiment of Artillery (and Commonwealth equivalents).

                              (Info from 24th Missile Regt RA Website - Thanks Phill)