27. The diphthongs

The diphthongs. Of the four diphthongs, two, the ए e and the ओ o, are in great part original Indo-European sounds. In the Sanskrit, they wear the aspect of being products of the increment or strengthening of इ i and उ u respectively; and they are called the corresponding guṇa-vowels to the latter (see below, 235 ff.). The other two, ऐ āi and औ āu, are held to be of peculiar Sanskrit growth; they are also in general results of another and higher increment of इ i and उ u, to which they are called the corresponding vṛddhi-vowels (below, 235 ff.). But all are likewise sometimes generated by euphonic combination (127); and ओ o, especially, is common as a result of the alteration of a final अस् as (175).