Gradual

[Sarah]

Proceeding by steps or degrees; advancing, step by step, as inascent or descent or from one state to another; regularlyprogressive; slow; as, a gradual increase of knowledge; a gradualdecline.Creatures animate with gradual life Of growth, sense, reason, allsummed up in man. Milton.

[PussyCat]

Taking place or progressing slowly or by degrees.

[Jessica]

happening or changing slowly over a long period of time or distance: