Vestige

Noun

1. A mark left on the earth by a foot.
2. A faint mark or visible sign left by something which is lost, or has perished, or is no longer present.

   "the vestiges of ancient magnificence in Palmyra"

3. A vestigial organ; a non-functional organ or body part that was once functional in an evolutionary ancestor.
4. The remaining portion of a partially suppressed sideband.