GRADUAL, advancing or taking place by degrees or step by step ; hence used of a slow progress or a gentle declivity , or slope, opposed to steep or precipitous.
As a substantive, "gradual" is used of a service book of the Roman Catholic Church containing certain chants, called "graduals," sung at the service of the Mass after the reading or singing of the Epistle.
For the so-called Gradual Psalms, cxx.–cxxxiv., the "songs of degrees," LXX., co8ai rcov ava/3aOµWV.