invariable
1. [ adjective ] not liable to or capable of change
Examples:

"an invariable temperature" "an invariable rule" "his invariable courtesy"

Related terms: variable changeless invariant hard-and-fast hard-and-fast fixed-income consistent constant
Similar spelling:   invariably
  invariance
  in_parallel
  invariant
  invariability
  in_private
  inoperable
  infringe
  in_brief
  infuriate
  infrared
  inebriety
  inebriate