In 1981, Hopper proposed to divide all Indo-European languages into Decem and Taihun groups, according to the pronunciation of the numeral '10', by analogy with the Centum-Satem isogloss, which is based on the pronunciation of the numeral '100'.
En 1981 Hopper propuxo dividir todas as linguas indoeuropeas nos grupos decem e taihun, de acordo coa pronuncia do numeral 10, por analoxía coa isoglosa centum-satem, que se basea na pronuncia do numeral 100.