Royal Navy type numbers preserve role-based bands

What do numbers such as Type 83 and Type 45 mean?

The Royal Navy assigned number bands to broad roles, with 81-99 denoting general-purpose warships capable of air defence, land attack, anti-submarine work, and independent operations.

Royal Navy type numbers were allocated in bands associated with broad roles. The ranges given here are 11-30 for anti-submarine frigates, 31-40 for general-purpose escorts, 41-50 for anti-aircraft frigates and destroyers, and 61-80 for aircraft-direction frigates. The 81-99 band is described as general-purpose warships combining air defence, land attack, and anti-submarine work. The distinction drawn is that an escort primarily supports a task force, while a warship in the latter band can also conduct independent operations. Reuse of the aircraft-direction range or a return to earlier numbers is suggested as a future possibility, not an announced numbering change. Type 83's number is therefore presented as a clue to its intended range of duties.