The five-vowel system of Indo-European is reduced to four by the merger of inherited o with other vowels, so that Hittite, Lycian, and probably Palaic show four vowels: a, e, i, and u. Luwian reduces this further to a, i, and u by merging e usually with a, but under certain conditions with i. The attested o vowel of Lydian is secondary. Hittite, Palaic, and Luwian preserve a contrast between short and long vowels, but Lycian and Lydian probably do not. The latter two languages develop distinct nasalized vowels /ẽ/ and /ã/. Only Hittite preserves in a significant way the vowel gradation known as “ablaut” (compare English sing, sang, sung), as with ēs-tsi ‘is’ versus as-antsi ‘are.’

The Anatolian languages reduce the three contrasting series of stop consonants inherited from Proto-Indo-European to two. One of these represents etymological voiceless stops and the other voiced stops, but the pronunciation in the attested languages is debatable. As first argued by linguist Jerzy Kuryłowicz in 1927, Hittite (as well as Palaic and Luwian) provides in the form of a consonant h(h) direct evidence for the “laryngeal” consonants reconstructed for Proto-Indo-European on purely internal grounds by linguist Ferdinand de Saussure in 1879. Study of the details of the development of these guttural (or pharyngeal) fricatives in Anatolian continues.

Lexical data

Click Here to see full-size tableSome examples of correspondences in vocabulary are given in the table. The oft-cited false impression that Hittite has replaced much of its vocabulary with borrowings from non-Indo-European languages is due to the peculiar nature of the preserved texts. Most of these describe the state cult or private rituals, areas of life where foreign influence on Hittite culture was unusually strong. Careful analysis shows that roughly 80 percent of Hittite core vocabulary is inherited from Proto-Indo-European, and the limited available evidence suggests a similar figure for the other languages.

Relationship with the other subgroups

The Anatolian languages of the 2nd millennium bce are the oldest Indo-European languages attested. The traditional picture of Indo-European thus faces a serious challenge in the apparent absence in Anatolian of such features as the feminine gender for nouns, the subjunctive and optative moods, and the verb tenses aorist (usually indicating simple past ‘ran’) and perfect (indicating an attained state ‘has run’) known from other archaic Indo-European languages.

There have been two major responses to this dilemma. One approach has sought to show that Anatolian inherited but lost all the categories named above (perhaps preserving a few crucial remnants). A radically opposing viewpoint, widely known as the “Indo-Hittite” hypothesis, holds that Anatolian and Proto-Indo-European, the reconstructed source of all other Indo-European languages, are collateral (same-generation) descendants of a still earlier linguistic stage, Indo-Hittite, that lacked these characteristics. This perspective posits that the absence of these grammatical features in Anatolian reflects its direct descent from the earlier Indo-Hittite stage.

This issue is far from settled, but it is unlikely that either of the models just described is valid in their extreme form. There is growing evidence that categories like the feminine gender and the aorist tense are reflected in Anatolian, but not in the form in which they have traditionally been reconstructed for Proto-Indo-European. Some specialists take this to show that speakers of the forerunner of the Anatolian languages separated from the common prehistoric speech community a few generations or a few centuries before other groups. However, no single viewpoint can be said to represent a consensus of scholars in the field.