noun, noun which may take the genitive case particle 'no'
world-leading; among the world's best
Used to describe something that ranks among the top in the world, often in a specific field or category.
日本は世界有数の長寿国だ。
Japan is one of the world's leading countries in longevity.
この大学は世界有数の研究機関として知られている。
This university is known as a world-leading research institution.
世界一 means 'number one in the world', while 世界有数 means 'among the world's best' without specifying a single top rank.
Compound of 世界 (world) and 有数 (prominent, leading). The exact historical derivation is uncertain, but the combination straightforwardly conveys 'world-leading'.