ra·dix 
(rādĭks)
(rādĭks)n. pl. rad·i·ces (rădĭ-sēz′, rādĭ-) or ra·dix·es
1. Biology A root or point of origin.
2. Abbr. rad. Mathematics The base of a system of numbers, such as 2 in the binary system and 10 in the decimal system.
[Latin rādīx, root; see wrād- in the Appendix of Indo-European roots.]