How did Latin verb forms change from earlier Indo-European forms?

The evolution of Latin verb forms from Proto-Indo-European (PIE) involved significant restructuring of the inherited system. While Latin retained the fundamental PIE personal endings used to express person and number, it underwent complex changes in aspect, mood, and voice.

Key developments include:

• Aspect and Tense: PIE relied on three distinct aspects—imperfective, perfective, and stative—which were not always predictable from one another. Latin reorganized these into a more systematic tense-aspect framework. For instance, the PIE stative aspect (the perfect) evolved into the Latin perfect tense, which merged functions of the original perfective (aorist) and stative aspects.12
• Voice: Latin maintained the distinction between active and mediopassive voices, notably preserving the passive endings in -r (e.g., vincitur), a feature shared with other languages like Celtic and Hittite.3
• Mood: Latin continued the use of mood suffixes to express distinctions such as the subjunctive, which evolved from PIE forms used for predictions or wishes.14
• Simplification: Over time, Latin moved away from the complex synthetic constructions of PIE, eventually favoring analytic forms in Vulgar Latin, where prepositions and word order began to replace older, more rigid inflectional systems.5