-nna is the “light” form used with verbal forms of the suffix conjugation, -yya is the “heavy” form. The “light” form used with verbal forms the prefix conjugation is -a, with the final consonant of the base doubled. The “heavy” suffixes are used with 2 fem. sg, all the plural and impersonal verbal forms, the “light” suffixes are used in all the other cases (Bulakh–Kogan 2013b:105).