Published online by Cambridge University Press: 22 April 2026
The metrical distribution of Rigvedic doublets like dyáus and diyáus is one of the foundations of Edgerton's theory of Proto-Indo-European semivowel alternation. The metrical distribution of the forms covered by Edgerton's theory is here compared with the distribution of words having different phonological structure but identical metrical shape, and it is seen that there is no difference between their distributions in statable metrical environments. In addition, a number of constraints on the incidence of Rigvedic semivowel alternation are pointed out, such as its strict limitation to the vocoid semivowels y and v, and it is argued that these constraints are difficult to account for in terms of the Sievers–Edgerton hypothesis. Rigvedic evidence provided the principal testimony for Edgerton's formulation of his hypothesis of semivowel alternation, but it is shown here, on the basis of the same text, that in its usually accepted form the Sievers–Edgerton hypothesis is neither necessary nor sufficient to account for the observed behavior of post-consonantal semivowels in word-initial position.