Conceptually, "sovereignty" is "primary" power or independent right without accountability to any other - autonomy, freedom from external control.
The term "sovereign" (adjective) is used on the international level to identify "primary" national entities that are without subordination to any other, having coequal standing. In simplistic terms, sovereign nations may be thought of as political persons having the capacity to own property and enter into contracts with other sovereigns on the international level. Individuals and political subdivisions are not recognized on the international level as coequal in status with sovereigns.
A "sovereign" (noun) is an individual who embodies national sovereignty. Monarchs and Emperors, for instance, were once described as the "font from whom all power and authority flows." Historically, the "sovereign" was similar in role to the pater familias of a national "family." The status of all other individuals within the nation was subordinate or "subject" to the sovereign in his/her regal capacity as the "Crown." Commonly, "sovereigns" have ruled by "divine right," by inherited right, and by right of force.
As stated by the Court in Glass v. The Sloop Betsey, 3 Dall 6 (1794):
"In Europe, the executive is almost synonymous with the sovereign power of a State; and generally includes legislative and judicial authority. ..."