The basic alternations

This chapter is a kind of bridge: its subject is phonology and morphology intertwined, with segmental and suprasegmental connections. It also introduces some of the more complicated aspects of IE historical linguistics; some knowledge of these areas is needed for understanding what would otherwise be highly puzzling features of morpheme-and word-shape in IE languages, including Old English.

As an introduction, consider the following IE cognates:

(On the forms in initial /s-/ see §5.6.)

These obviously contain ‘the same’ IE root, with a basic sense like ‘cover’; and the consonantal ‘skeleton’ easily reconstructs as */tVg-/. This gives L, Lith, Olr /tVg-/, and by Grimm's Law (§2.3) Gmc */θVk-/, which by regular changes gives all the Germanic shapes listed.

So much then for the consonants. But it seems impossible to reconstruct a unique ancestral vowel. IE */e/ would account for teg-ō, o-steg-nąti, teg; but tog-a, stóg-as, þak, dah, þæc require */o/, and tēg-ula, tēc-tum require */e:/. If no single IE vowel could give all these reflexes, what is the shape of the ancestral root? Or is this the right question to ask?