Proto-Anatolian is the proto-language from which the ancient Anatolian languages emerged. As with almost all other proto-languages, no attested writings have been found; the language has been reconstructed by applying the comparative method to all the attested Anatolian languages as well as other Indo-European languages. Craig Melchert, an expert on the Anatolian languages, estimates that Proto-Anatolian began to diverge c. 3000 BC, in any case no later than c. 2500 BC.
Phonology
For the most part, Proto-Anatolian has been reconstructed on the basis of Hittite, the best-attested Anatolian language. However, the usage of Hittite cuneiformwriting system limits the enterprise of understanding and reconstructing Anatolian phonology, partly from the deficiency of the adopted Akkadian cuneiform syllabary to represent Hittite phonemes and partly from Hittite scribal practices. It is especially pertinent to what appears to be confusion of voiceless and voiced dental stops, in which signs -dV- and -tV- are employed interchangeably in different attestations of the same word. Furthermore, in the syllables of the structure VC, only the signs with voiceless stops are usually used. Distribution of spellings with single and geminated consonants in the oldest extant monuments indicates that the reflexes of Proto-Indo-European voiceless stops were spelled as double consonants and the reflexes of PIE voiced stops as single consonants. This regularity is the most consistent in the case of dental stops in older texts; later monuments often show irregular variation of this rule.
Vowels
Common Anatolian preserves the PIEvowel system basically intact. Some cite the merger of PIE */o/ and */a/ as a Common Anatolian innovation, but according to Melchert that merger was a secondary shared innovation in Hittite, Palaic and Luwian, but not in Lycian. Concordantly, Common Anatolian had the following short vowel segments: */i/, */u/, */e/, */o/ and */a/. Among the long vowels, */eː/ < PIE *ē is distinguished from */æː/ < PIE *eh₁, with the latter yielding ā in Luwian, Lydian and Lycian. Melchert had also earlier assumed a contrast between a closer mid front vowel */eː/ < PIE *ey and a more open */ɛː/ < PIE *ē, but the examples are few and can be accounted for otherwise. The status of the opposition between long and short vowels is not entirely clear, but it is known for certain that it does not keep the PIE contrast intact, as Hittite spelling varies in a way that makes it very hard to establish whether vowels were inherently long or short. Even with older texts being apparently more conservative and consistent in notation, there are significant variations in vowel length in different forms of the same lexeme. It has been thus suggested by Carruba that the so-called scriptio plena represents not long vowels but rather stressed vowels, reflecting the position of free PIE accent. Carruba's interpretation is not universally accepted; according to Melchert, the only function of scriptio plena is to indicate vowel quantity; according to him the Hittite a/ā contrasts inherits diphonemic Proto-Anatolian contrast, */ā/ reflecting PIE */o/, */a/ and */ā/, and Proto-Anatolian */a/ reflecting PIE */a/. According to Melchert, the lengthening of accented short vowels in open syllables cannot be Proto-Anatolian, and the same goes for lengthening in accented closed syllables.
Consonants
One of the more characteristic phonological features common to all Anatolian languages is the lenition of the Proto-Indo-European voiceless consonants between unstressed syllables and following long vowels. The two can be considered together as a lenition rule between unstressed morae, if long vowels are analyzed as a sequence of two vowels. All initial voiced stops in Anatolian eventually merge with the plain voiceless stops; Luwian, however, shows different treatment of voiced velar stops *G- and unvoiced velar stops *K-, showing that this was a late areal development, not a Proto-Anatolian one. Proto-Anatolian is the only daughter language of Proto-Indo-European to directly retain the laryngeal consonants. The letter ‹ḫ› represents the laryngeal *h₂ and probably but less certainly also *h₃. The sequences *h₂w and *h₃w yield a labialized laryngeal *ḫʷ. In addition to the laryngeals, Common Anatolian was long also thought to be the only daughter to preserve the three-part velar consonant distinction from Proto-Indo-European. The best evidence for this was thought to come from its daughter language Luwian. However, Melchert disputes this and categorizes Anatolian as a centum branch. The voiced aspirated stops lost their aspiration over time and merged with the plain voiced stops. The liquids and nasals are inherited intact from Proto-Indo-European, and so is the glide *w. No native Proto-Anatolian words begin with *r-. One possible explanation is that it was true in Proto-Indo-European as well. Another is that it is a feature of languages from the area in which the daughter languages of Proto-Anatolian were spoken.
Morphology
According to Fortson, Proto-Anatolian had two verb conjugations. The first, the mi-conjugation was clearly derived from the familiar Proto-Indo-European present tense endings. The second, the ḫi-conjugation appears to be derived from the Proto-Indo-European perfect. One explanation is that Anatolian turned the perfect into a present tense for a certain group of verbs while another, newer idea is that the ḫi verbs continue a special class of presents which had a complicated relationship with the Proto-Indo-European perfect.
