NOUN STEMS AND THEIR HIERARCHY IN THE NORTHERN SIRVINTISKIAI SUBDIALECT Summary In the Northern Sirvintiskiai subdialect, a noun stem is treated as independent if it differs from other stems in at least the ending of one case form. With regard to this condition, the i stem and the consonant stem are subdivided into the masculine and feminine gender stems. In the subdialect, traditional stems have been better retained in nouns having mobile stress. Due to shortening of unstressed long vowels, partial stress retraction and other reasons, barytone nouns have deviated to a great extent from the primary paradigms. In the Northern Sirvintiskiai subdialect, the number of noun stems is lower than that in standard Lithuanian and in the majority of its dialects, as iu , ia 1 and ia 2 stem nouns are inflected in a totally homogeneous way, i. e. according to the ia 2 stem implicative model. Nouns of mobile stress have a , ia 2 , u , ā , i ā , ē , i m , i f , C m and C f stems. Barytone stress nouns only have six stems, i. e. a , ia 2 , u , ā , ē , and i f stems. The i ā stem has coincided with the ē stem. Meanwhile, the i m , C m and C f stems are not found in words with barytone stress. Hierarchic stem grouping “trees” that are produced using three methods (the maximum, minimum and average methods) indicate existence of three different types of noun declension: the masculine model (embracing the a , ia 2 and u stems), the feminine model (the ā and i ā stems) and the mixed model (the i m , i f , C m and C f stems). The ē stem is isolated: it embraces feminine gender nouns, yet according to declension there is a tendency towards the mixed declension type to a slightly greater extent. The a , ia 2 , ā , i ā and ē stems are stable. They do not decline or rarely decline from their implicative models, and have no additional (complementary) paradigms. They are all (except for the i ā stem) highly productive, open, constantly enriched with words from standard Lithuanian, other dialects and languages, and also with words having unstable stems. Unstable stems are as follows: u , i m , i f , C m and C f .They are unproductive, and often have complementary paradigms and lose part of words belonging to them.