We can find such nominal stems as alternate like oki～okin ≪girl, daughter≫, kuu～kuun ≪person≫, qa～qan ≪emperor≫, qatu～qatun ≪emperess≫, irge～irgen ≪the people≫, sai～sain ≪good, the good≫ in the language of "the Secret History of Mongols" and the author of this paper tried to find the defference of meaning between the stems with -n, for exmple okin, kuun, qan, qatun. irgen, sain and the stems without -n, for exmple oki, kuu, qa, irge, saj.
As a result of this research, the author has been convinced that on the stage of old Mongolian the stems with-n expressed the definite objects under the given context but the stems without-n, on the contrary, the indefinite objects under the given context.
The author of this line clarified this fact by showing a lot of exemples in this paper.