Merriam-Webster Collegiate Dictionary - gradual

 I. noun  Usage: often capitalized  Etymology: Middle English, from Medieval Latin ~e, from Latin gradus step; from its being sung on the steps of the altar  Date: 15th century  1. a book containing the choral parts of the Mass  2. a pair of verses (as from the Psalms) proper after the Epistle in the Mass  II. adjective  Etymology: Medieval Latin ~is, from Latin gradus  Date: 1658  1. proceeding by steps or degrees  2. moving, changing, or developing by fine or often imperceptible degrees  • ~ly adverb  • ~ness noun