The phonetic composition remains very hard to know for sure, because not all phonemes can be distincted from written documents. Supposedly, there were 9 vowels (all long and short, except short o), which could be reduced easily due to phonetic processes. The consonant mutations included *d > l, *c > dj, -rs- > -s'- etc. In general, Bactrian phonetics has features both seen in modern Pashto and in Middle Iranian Parthian and Sogdian.
In morphology, Bactrian went rather far from ancient languages than other Iranian tongues. The gender disappeared, only 2 noun cases were preserved (direct and indirect), the ancient inflected forms of the past tense were replaced. The language used a definite article i.
Bactrian was completely assimilated by the Persian language, which spread in Tocharistan. This process is believed to take place until the 12th century.