sub·in·dex /ˌsʌbˈɪnˌdɛks/ 分指數
Sub·in·dex n.; pl. Subindices Math. 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. ◄ ►