семя
Kirusi[hariri]
Asili[hariri]
The so-called н-declension of this and nine other similar neuter nouns stems from the fact that the word-final -я was the nasal vowel Ѧ, ѧ (little yus) in Old Church Slavonic, resulting in the -ен- before all the case endings in the modern language.
Nomino[hariri]
семя (sémja, 'n', семена, semená, Kigezo:p) (ru)