A sovereign state is a country that has its own government and has full control over its own territory. It is not controlled by any other country or external authority. Full definition
Ideally, international law should also extend far beyond these traditional provisions for preserving the integrity and independence of sovereign states, into the domain of universal human rights. (religion-online.org)
If you buy treasury bonds issued by sovereign states in their own currency then the default risk is extremely low. (money.stackexchange.com)
Their approach is indicative of a trend towards holding national governments accountable in law where they enter into contractual relationships with private citizens and corporations by limiting the protection afforded by sovereign state immunity. (newlawjournal.co.uk)