The article is devoted to the study of typological peculiarities of morphemic word structure in two languages of different types -analytical English and agglutinative Buryat -in relation to the significance of language's degree of lexicality and grammaticality as its typological determinant. It proves, in particular, the significance of studying the morphemic word structure when separating semiological classes of words from parts of speech; it also determines the grammaticality index and degree of synthesis of a word, as well as discovers most typical models of morphemic "word-in-general" structure, of semiological classes and of separate parts of speech, particularly nouns and verbs, which form the basic opposition of parts of speech. © 2017 Institute of Linguistic. All rights reserved.