before vowels dodec-, word-forming element used in technical compounds of Greek origin, signifying "twelve," from Latinized form of Greek dōdeka "twelve" (short for duodeka), from duo "two" (from PIE root *dwo- "two") + deka "ten" (from PIE root *dekm- "ten"). Compare dozen.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit dvau, Avestan dva, Greek duo, Latin duo, Old Welsh dou, Lithuanian dvi, Old Church Slavonic duva, Old English twa, twegen, German zwei, Gothic twai "two;" first element in Hittite ta-ugash "two years old."
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit dasa, Avestan dasa, Armenian tasn, Greek deka, Latin decem (source of Spanish diez, French dix), Old Church Slavonic deseti, Lithuanian dešimt, Old Irish deich, Breton dek, Welsh deg, Albanian djetu, Old English ten, Old High German zehan, Gothic taihun "ten."