Among the ruling principles which have determined the phy siognomy of Slavonic speech are : the rigorous division of the vowels into a prepalatal and a postpalatal series—this having big consequences for the subsequent fate of the preceding con sonants—and a system of word division which tolerated only open syllables. Except in initial position, the I.E. vowels generally underwent slight changes, but the loss of labialisation suffered by long u, and the levelling of short o and a under 6, are character istically Slavonic. The change of short it and which were not kept distinct everywhere, led to great alterations in the syllabic character of words and has tended, especially in Polish, to pro duce difficult consonantal groups. The distinction between voiced and voiceless sounds continued without interruption, and the nasal and liquid consonants, when initial or intervocalic, also per sisted unchanged. Numerous sibilants (of the type of English witch and wits) arose at different periods, after the separation from Baltic but before our earliest Slavonic records, and the com bination of vowels with following nasal or liquid consonants, when the latter were followed by a consonant, conditioned the f orma tion of nasal vowels. To sum up, the general persistence of vowels in positions where vowels already existed in an I.E. word, and the conservative behaviour of consonants make it possible to recognize, with a minimum knowledge of historical grammar, the fundamental connection of a Slavonic word with its cor responding I.E. prototype. Nebese, compared with its Greek equivalent z44)ovs is much the nearer to the form postulated for Indo-European. The complicated phenomena of vowel gradation (Ablaut), as presented by Slavonic, in the main answer to the Indo-European.
The -o-, -a- and -i- declensions have gained at the expense of the consonantal and -fi- stems, and phonetic or analogical change has caused many cases to coincide, especially in the dual. The adjective, when definite, receives a pronominal element, at first clearly distinguishable, but later unrecognizably merged in the body of the word. There is neither a definite nor an indefinite article. Of the two I.E. types of inflexion, the thematic and the athematic, the latter has lost ground to the former, and the -s aorist early tended to be lost in favour of a more transparent thematic formation.
The verb, indeed, has lost most of the I.E. voices, moods and tenses. The passive only survives in the present and past parti ciples; of the finite moods there are left but the indicative and optative (nearly always used as an imperative) ; its only old tenses are the present and the aorist, to which it has added an imperfect of its own. There is an infinitive and a supine, both representing cases of an original verbal noun. Of active participles
there are a present and a past and a second past participle in -1 (cf. Latin bibulus), used in making compound tenses. The verb has two stems ; from the present are formed the indicative present and imperfect, the imperative and the active and passive present participles. All other forms are based upon the infinitive stem. The primary personal endings continue those of I.E. in a form recognizable to-day, but the secondary endings have lost their final consonants by phonetic change. The aorist has no augment and has been replaced by a periphrastic formation with the -1- participle in nearly all the modern languages, The past participle passive is formed with -t- or -n-. (Cf. Latin plenus and P/etus.) The I.E. future having been lost, futurity is expressed by auxiliary verbs as in the Romance languages, The passive is expressed either by the use of the passive participles or by the reflexive pronoun, which can refer to the 1st and 2nd persons as well as to the 3rd.
In the use of the verbs the development of "aspects" makes up for the few tenses, All verbs fall into two great divisions, imperfective, which express the continuance of an action, without regard to its beginning and end, and perfective, which express the points of beginning or ending. The continuance of an action may be unbroken or may consist in a succession of like acts. Accord ingly, imperfective verbs are divided into durative and iterative, and again the repeated acts expressed by the iterative can either, each of them, be momentaneous, or each have some continuance, or can even express the occasional repetition of groups of momentaneous actions.
Among perfective verbs we have (i) momentaneous, expressing action which has no continuance, (2) finitive, expressing not the continuance of the action, though there has been that, but its end or completion, and (3) ingressive, expressing the moment of beginning an action.
As perfective verbs do not express continuance, an idea implied in the present, they do not need a present form, which is there fore used for perfective futures. Similarly the aorist is usual with perfective, but the imperfect with imperfective verbs. If a durative verb is compounded with a preposition, it becomes per fective. (Cf. English "sit," which is usually imperfective, with "sit down.") Some Slavonic languages (notably Czech) have extended the possibilities of the aspects still further, but others, e.g., Slovene, have made simplifications and permit the union of a perfective infinitive with an auxiliary, to form the future.