Etymology tree Esperanto tri Proto-Indo-European *déḱm̥ Proto-Hellenic *dékə Ancient Greek δέκα (déka)der. Proto-Indo-European *déḱm̥ Proto-Italic *dekəm Latin decemder. Esperanto dek Esperanto kvin Esperanto -a Esperanto tridek-kvina From tri + dek + kvin + -a.