Why did the United Nations use the temporary name former Yugoslav Republic of Macedonia?

The United Nations used the temporary designation "the former Yugoslav Republic of Macedonia" due to strong opposition from Greece regarding the country's constitutional name.12

Following its independence from Yugoslavia in 1991, the newly formed state sought international recognition under the name "Republic of Macedonia." However, Greece—which contains its own region also named Macedonia—strenuously objected to the use of the name by its neighbor. Greece claimed a monopoly on the term, citing its historical continuity with the ancient Macedonians and Alexander the Great, and argued that the name implied territorial claims over the Greek region.2

In an effort to resolve the dispute and facilitate the country's entry into international organizations, the UN mediated long-running negotiations between the two nations. This "name issue" persisted for decades until the 2018 Prespa Agreement, which resulted in the country officially adopting the name Republic of North Macedonia in 2019.123