According to the generally accepted definition of St. Thomas Aquinas, an ordinance of reason, framed for the common good, by those who have care of the community as a whole, and promulgated (Summa theologiae, I-II, q. 90, a. 4). 

Eternal Law.— The divine intellect as directing all created things to their proper end; it is the ultimate or supreme rule of morality. 

Natural Law (also called Natural Moral Law).— The morally fitting ends known by reason, rooted in the nature of rational creatures, and derived from the eternal law, measuring the conduct of rational creatures. The natural law is the rational creature’s rational participation in the eternal law.  Using a somewhat looser terminology, the Church Fathers and a number of later theologians, often connect the natural law to the Ten Commandments as well.  In the modern period, the natural law often was understood as those moral norms which are cross-confessionally knowable or even knowable without the supposition of God’s existence. 

Divine Law.— The divinely revealed providential economy of salvation, considered either as referring to the Old Covenant or the New Covenant and therefore subdivided as “Old Law” and “New Law.”  The Old Law included moral, ceremonial, and judicial precepts.  The moral precepts continue in the state of the New Law.  The ceremonial and judicial precepts are a kind of divine positive law, specifying aspects of religion and justice in the society of the Chosen People of Israel.  The “New Law” is primarily, but not exclusively, an internal law of beatifying perfection through life lived according to the infused theological and moral virtues, perfected by the gifts of the Holy Spirit. 

Human Law.— Positive laws framed by human governments.   Human law is an extension and determination of the natural law. 

Law of Nations (ius gentium).— Generally accepted moral truths held by all morally civilized peoples.  Some theorists hold that it is a kind of positive law, others that it is a concretization of the natural law.