Proto-Greek inherited the augment, a prefix "e-", to verbal forms expressing past tense. That feature is shared only with Indo-Iranian and Phrygian (and to some extent, Armenian), lending some support to a "Graeco-Aryan" or "Inner PIE" proto-dialect. However, the augment down to the time of Homer remained optional and was probably little more than a free sentence particle, meaning "previously" in the proto-language, which may easily have been lost by most other branches. Greek, Phrygian, and Indo-Iranian also concur in the absence of "r"-endings in the middle voice, in Greek apparently already lost in Proto-Greek.