Judicial, judiciary, juridical, juristic are comparable because of verbal confusion and because all imply some connection with courts of law.
Judicial, by far the most common of these adjectives both in legal and in general use, often implies a direct reference to the courts of justice, the judge who presides over a court of justice, or the judges who form such a court. The term is also used in distinction from executive, legislative when applied to that one of the powers, departments, or functions of the government which is associated with a court (as the United States Supreme Court), which gives definitive decisions on questions of law or interprets the constitution or basic law.
In extended use judicial is applied especially to a type of mind, mental activity, or manner suggestive of that of a judge (as in detachment or fair-mindedness) or appropriate to a judge or court of justice (as in orderliness and seriousness of procedure).
Judiciary is occasionally used in place of judicial, especially when it suggests reference to the courts in general and to the administration of justice as a whole. In current usage, however, judiciary occurs predominantly as a substantive, with judicial its corresponding adjective. The two words juridical and juristic imply a connection with the law, especially as it is administered in the courts, rather than with the judges or those who settle questions of law. Often these terms come close to legal in meaning, but in learned use they are more restricted in significance.
Both terms, but especially juridical, imply a reference to the law as it appears to learned lawyers and judges—that is, as a highly complex and involved body of principles, statutes, decisions, and precedents requiring vast knowledge, skill in interpretation, and a keen logical mind in those who put it to use; therefore, the term often means characteristic of, determinable by, or useful to a person with such knowledge and skill.
Juristic implies rather a reference to the science of law.