the teeth rather than against the alveolar ridge. Vowels Russian has five or six vowels in stressed syllables, , and in some analyses , but in most cases these vowels have merged to only two to four vowels when unstressed: (or ) after hard consonants and after soft ones. These vowels have several allophones, which are displayed on the diagram to the right. Grammar Russian has preserved an Indo-European synthetic-inflectional structure, although considerable leveling has occurred. Russian grammar encompasses: a highly fusional morphology a syntax''' that, for the literary language, is the conscious fusion of three elements: a polished vernacular foundation; a Church Slavonic inheritance; a Western European style. The spoken language has been influenced by the literary one but continues to preserve characteristic forms. The dialects show various non-standard grammatical features, some of which are archaisms or descendants of old forms since discarded by the literary language. In terms of actual grammar, there are three tenses in Russian past, present, and future and each verb has two aspects (perfective and imperfective). Russian nouns each have a gender either feminine, masculine, or neuter, chiefly indicated by spelling at the end of the word. Words change depending on both their gender and function in the sentence. Russian has six cases: Nominative (for the grammatical subject), Accusative (for direct objects), Dative (for indirect objects), Genitive (to indicate possession or relation), Instrumental (to indicate 'with' or 'by means of'), and Prepositional (used after the locative prepositions в "in", на "on", о "about", при "in the presence of"). Verbs of motion in Russian such as 'go', 'walk', 'run', 'swim', and 'fly' use the imperfective or perfective form to indicate a single or return trip, and also use a multitude of prefixes to add shades of meaning to the verb. Such verbs also take on different forms to distinguish between concrete and abstract motion. Vocabulary See History of the Russian language for an account of the successive foreign influences on Russian. The number of listed words or entries in some of the major dictionaries published during the past two centuries, are as follows: History and examples The history of the Russian language may be divided into the following periods: Kievan period and feudal breakup The Moscow period (15th–17th centuries) Standard national language Judging by the historical records, by approximately 1000 AD the predominant ethnic group over much of modern European Russia, Ukraine, and Belarus was