Grammatical Gender

[Dobri]

... In Slavic languages, -l and -il (EVA m) are the most clear indication of singular masculine past and future participle. For the female gender, -a is the most frequent suffix for nouns and for verbs, however since words occur in different declinations, and different conjunction, the suffixes are different...

Also, plural forms in Slavic languages end often in -e which would require using mainly vowels for the last suffix symbols in the cipher manuscript.