Which features of Anatolian grammar differ from those of many other early Indo-European languages?

The Anatolian languages, which represent the oldest attested Indo-European languages, exhibit several grammatical features that distinguish them from other archaic Indo-European branches.1

Notable Differences

The most significant departures from the traditional reconstruction of Proto-Indo-European include:

• Gender System: Anatolian lacks the feminine gender for nouns, instead utilizing a system based on animate (common) and inanimate (neuter) categories.12
• Moods and Tenses: These languages do not feature the subjunctive or optative moods, nor do they possess the aorist or perfect tenses typically found in other early Indo-European languages.1
• Ergativity: An innovation in Anatolian is that the nominative case of a neuter noun cannot serve as the subject of a transitive verb; instead, an "ergative" case is used for this function.2
• Sentence Structure: Anatolian languages frequently attach strings of enclitic pronouns and various particles to the first accented word of a sentence, a practice they exploited to a much greater degree than other early Indo-European groups.2

These differences have led some scholars to propose the "Indo-Hittite" hypothesis, which suggests that Anatolian and other Indo-European languages are collateral descendants of an earlier linguistic stage that lacked these specific features.1