To become a lawyer and practice law in most states and countries, a person must first obtain a law degree. While in most common law countries a Bachelor of Laws (or LL.B.) is required, the U.S. requires a professional doctorate, or Juris Doctor, to practice law.If a person wishes to gain specialized knowledge through research in a particular area of law, he or she can continue his or her studies after an LL.B or J.D. in an LL.M. program. The word legum is the genitive plural form of the Latin word lex, which means "of the laws". When used in the plural, it signifies a specific body of laws, as opposed to the general collective concept embodied in the word jus, from which the words "juris" and "justice" derive.The highest research degree in law is the S.J.D. (or J.S.D., depending on the institution), and it is equivalent to the Doctor of Philosophy in Law (PhD or DPhil depending on the law school in UK), Doctorat en Droit (in France), or the Doktor der Rechtswissenschaften (Dr.iur.) in Germany. There are also variant doctoral degrees, such as the D.C.L. (Doctor of Civil Law) degree bestowed by McGill University in Montreal. Most schools require an LL.M. before admission to a SJD or a PhD in law degree program. Like the PhD, the SJD degree generally requires a dissertation that is graded (often by two graders), orally defended (by an exam known as Viva) and then often published as a book or series of articles."Doctor of Laws" (LL.D.) degree in the United States of America is usually an honorary degree. The research doctorate in the field of law in the United States of America is called "Doctor of Juridical Science" or in its Latin expression-"Scientiae Juridicae Doctor" (S.J.D.), which is the most advanced degree in the field of law in the United States of America.