-nä is the “light” form used with verbal forms of the suffix conjugation, -änä is the “light” form used with verbal forms of the prefix conjugation, -nnä is the “heavy” form. 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).