Subindex
Pronunciation : Sub*in"dex
Part of Speech : n.;
Definition : Defn: A number or mark placed opposite the lower part of a letter or symbol to distinguish the symbol; thus, a0, b1, c2, xn, have 0, 1, 2, and n as subindices.
pl. Subindices (. (Math.)
Source : Webster's Unabridged Dictionary, 1913