Vocabulary and Definitions of Law:

The Roman Law Foundations

Detail from Tomb of Mondino de' Liuzzi ( 1326),

 sculpted by Roso (Boso) da Parma,

Church of San Vitale, Bologna

The Ius commune

Vocabulary of Law: Ius (iuris), Lex (legis), Droit, Derecho, Diritto, Direito, Recht, Prawo, Ustawa

Custom (Consuetudo - Mos [moris, mores]), written and unwritten
 
Legislation: statutes, constitutions, plebiscites, laws, ordinances

Transcendental legal systems: Ius gentium, ius naturale, religious law, moral and ethical norms
 

Definitions of Law:  Definitions of Law 1     Definitions of Law 2     Definitions of Law (Foreign)

Positive law (ius positivum), John Austin (legal positivism)

Jefferson on Natural Law and Natural Rights

Ken Pennington, Lex naturalis and Ius naturale
 

General Differences between the Common Law and Civil Law Tradition (The Ius commune)

 

1. Codification - Case Law, Court Decisions, and Stare decisis

2. Role of Jurists (Lawyers and Jurists) 

3. Educational Methodology and Goals

4. Role of Judges: Arbitrator - Investigative

5. Procedure:  Adversarial - Inquisitorial

The best book on the differences between the civil and common law systems is John Henry Merryman, The Civil Law Tradition:  An Introduction to the Legal Systems of Western Europe and Latin America (2nd Edition; Stanford: Stanford University Press, 1985)