incremental

from WordNet (r) 3.0 (2006)

incremental
    adj 1: increasing gradually by regular degrees or additions;
           "lecturers enjoy...steady incremental growth in salary"

from The Collaborative International Dictionary of English v.0.48

Incremental \In`cre*men"tal\, a. (Biol.)
   Pertaining to, or resulting from, the process of growth; as,
   the incremental lines in the dentine of teeth.
   [1913 Webster]