A more thorough explanation:

A nomen is a personal name, particularly in Roman law. In ancient Rome, citizens had three names: a praenomen (first name), a nomen (family name), and a cognomen (surname). For example, Julius Caesar's full name was Gaius Julius Caesar. The nomen is the name of the family group.

More broadly, a nomen can refer to any name. For example, "John" is a nomen.

A nomen collectivum is a collective name for a class of things. For example, "fruit" is a nomen collectivum because it refers to a group of different types of fruit.

A nomen generale is a general name or genus. For example, "dog" is a nomen generale because it refers to a group of different breeds of dogs.

A nomen juris is a legal name or designation. For example, "LLC" is a nomen juris because it is a legal designation for a type of business entity.

A nomen universitatis is a historical term for the name of a whole entity. For example, "Barony" is a nomen universitatis because it refers not only to the lands over which the rights of barony extend, but also to the rights themselves.