When a particular termination or suffix once acquired a special sense, it would be separated in thought from the stem to which it belonged, and attached in the same sense to other stems and other terminations. Thus in modern English we can attach the suffix -ize to almost any word whatsoever, in order to give the latter a transitive meaning, and the Gr. πόδεσσι, quoted above, really contains no less than three suffixes, -ες, -συ and -ι, the last two both denoting the locative, and coalescing, through σϝι, into a single syllable -σι. The latter instance shows us how two or more suffixes denoting exactly the same idea may be tacked on one to another, if the original force and signification of the first of them comes to be forgotten. Thus, in O. Eng. sang-estre was the feminine of sang-ere, “singer,” but the meaning of the termination has so entirely died out of the memory that we have to add the Romanic -ess to it if we would still distinguish it from the masculine singer. A familiar example of the way in which the full sense of the exponent of a grammatical idea fades from the mind and has to be supplied by a new exponent is afforded by the use of expletives in conversational English to denote the superlative. “Very warm” expresses little more than the positive, and to represent the intensity of his feelings the Englishman has recourse to such expressions as “awfully warm” like the Ger. “schrecklich warm.”
Such words as “very,” “awfully,” “schrecklich,” illustrate a second mode in which Indo-European grammar has found means of expression. Words may lose their true signification and become the mere exponents of grammatical ideas. Professor Earle divides all words into presentive and symbolic, the former denoting objects and conceptions, the latter the relations which exist between these. Symbolic words, therefore, are what the Chinese grammarians call “empty words”—words, that is, which have been divested of their proper signification and serve a grammatical purpose only. Many of the classificatory and some of the flexional suffixes of Indo-European speech can be shown to have had this origin. Thus the suffix tar, which denotes names of kinship and agency, seems to come from the same root as the Lat. terminus and trans, our through, the Sans. tar-āmi, “I pass over,” and to have primarily signified “one that goes through” a thing. Thus, too, the Eng. head or hood, in words like godhead and brotherhood, is the A.-S. hâd, “character” or “rank”; dom, in kingdom, the A.-S. dôm, “judgment”; and lock or ledge, in wedlock and knowledge, the A.-S. lâc, “sport” or “gift.” In all these cases the “empty words,” after first losing every trace of their original significance, have followed the general analogy of the language and assumed the form and functions of the suffixes with which they had been confused.
A third mode of representing the relations of grammar is by the symbolic use of vowels and diphthongs. In Greek, for instance, the distinction between the reduplicated present δίδωμι and the reduplicated perfect δέδωκα is indicated by a distinction of vowel, and in primitive Aryan grammar the vowel â seems to have been set apart to denote the subjunctive mood just as ya or i was set apart to denote the potential. So, too, according to M. Hovelacque, the change of a into i or u in the parent Indo-European symbolized a change of meaning from passive to active. This symbolic use of the vowels, which is the purest application of the principle of flexion, is far less extensively carried out in the Indo-European than in the Semitic languages. The Semitic family of speech is therefore a much more characteristic type of the inflexional languages than is the Indo-European.
The primitive Indo-European noun possessed at least eight cases—nominative, accusative, vocative, instrumental, dative, genitive, ablative and locative. M. Bergaigne has attempted to show that the first three of these, the “strong cases” as they are termed, are really abstracts formed by the suffixes -as (-s), -an, -m, -t, -i, -â and -ya (-i), the plural being nothing more than an abstract singular, as may be readily seen by comparing words like the Gr. ἔπο-ς, and ὄπε-ς, which mean precisely the same. The remaining “weak” cases, formed by the suffixes -sma, -sya, -syâ, -yâ, -i, -an, -t, -bhi, -su, -i, -a and -â, are really adjectives and adverbs. No distinction, for example, can be drawn between “a cup of gold” and “a golden cup,” and the instrumental, the dative, the ablative and the locative are, when closely examined, merely adverbs attached to a verb. The terminations of the strong cases do not displace the accent of the stem to which they are suffixed; the suffixes of the weak cases, on the other hand, generally draw the accent upon themselves.
According to Hübschmann, the nominative, accusative and genitive cases are purely grammatical, distinguished from one another through the exigencies of the sentence only, whereas the locative, ablative and instrumental have a logical origin and determine the logical relation which the three other cases bear to each other and the verb. The nature of the dative is left undecided. The locative primarily denotes rest in a place, the ablative motion from a place, and the instrumental the means or concomitance of an action. The dative Hübschmann regards as “the case of the participant object.” Like Hübschmann, Holzweissig divides the cases into two classes—the one grammatical and the other logical; and his analysis of their primitive meaning is the same as that of Hübschmann, except as regards the dative, the primary sense of which he thinks to have been motion towards a place. This is also the view of Delbrück, who makes it denote tendency towards an object. Delbrück, however, holds that the primary sense of the ablative was that of separation, the instrumental originally indicating concomitance, while there was a double locative, one used like the ablative absolute in Latin, the other being a locative of the object.
The dual was older than the plural, and after the development of the latter survived as a merely useless encumbrance, of which most of the Indo-European languages contrived in time to get rid. There are still many savage idioms in which the conception of plurality has not advanced beyond that of duality. In the Bushman dialects, for instance, the plural, or rather that which is more than one, is expressed by repeating the word; thus tu is “mouth,” tutu “mouths.” It may be shown that most of the suffixes of the Indo-European dual are the longer and more primitive forms of those of the plural which have grown out of them by the help of phonetic decay. The plural of the weak cases, on the other hand (the accusative alone excepted), was identical with the singular of abstract nouns; so far as both form and meaning are concerned, no distinction can be drawn between ὄπες and ἔπος. Similarly, humanity and men signify one and the same thing, and the use of English words like sheep or fish for both singular and plural shows to what an extent our appreciation of number is determined by the context rather than by the form of the noun. The so-called “broken plurals” of Arabic and Ethiopic are really singular collectives employed to denote the plural.
Gender is the product partly of analogy, partly of phonetic decay. In many languages, such as Eskimo and Choctaw, its place is taken by a division of objects into animate and inanimate, while in other languages they are separated into rational and irrational. There are many indications that the parent Indo-European in an early stage of its existence had no signs of gender at all. The terminations of the names of father and mother, pater and mater, for example, are exactly the same, and in Latin and Greek many diphthongal stems, as well as stems in i or ya and u (like ναῦς and νέκυς, πόλις and λῖς), may be indifferently masculine and feminine. Even stems in o and a (of the second and first declensions), though the first are generally masculine and the second generally feminine, by no means invariably maintain the rule; and feminines like humus and ὁδός, or masculines like advena and πολίτης, show that there was a time when these stems also indicated no particular gender, but owed their subsequent adaptation, the one to mark the masculine and the other to mark the feminine, to the influence of analogy. The idea of gender was first suggested by the difference between man and woman, male and female, and, as in so many languages at the present day, was represented not by any outward sign but by the meaning of the words themselves. When once arrived at, the conception of gender was extended to other objects besides those to which it properly belonged. The primitive Indo-European did not distinguish between subject and object, but personified objects by ascribing to them the motives and powers of living beings. Accordingly they were referred to by different pronouns, one class denoting the masculine and another class the feminine, and the distinction that existed between these two classes of pronouns was after a time transferred to the nouns. As soon as the preponderant number of stems in o in daily use had come to be regarded as masculine on account of their meaning, other stems in o, whatever might be their signification, were made to follow the general analogy and were similarly classed as masculines. In the same way, the suffix i or ya acquired a feminine sense, and was set apart to represent the feminine gender. Unlike the Semites, the Indo-Europeans were not satisfied with these two genders, masculine and feminine. As soon as object and subject, patient and agent, were clearly distinguished from each other, there arose a need for a third gender, which should be neither masculine nor feminine, but denote things without life. This third gender was fittingly expressed either by the objective case used as a nominative (e.g. regnum), or by a stem without any case ending at all (e.g. virus).
The adverbial meaning of so many of the cases explains the readiness with which they became crystallized into adverbs and prepositions. An adverb is the attribute of an attribute—“the rose smells sweetly,” for example, being resolvable into “the rose has the attribute of scent with the further attribute of sweetness.” In our own language once, twice, needs, are all genitives; seldom is a dative. The Latin and Greek humi and χαμαί are locatives, facillime (facillumed) and εὐτυχῶς ablatives, πάντη and ἄμα instrumentals, πάρος, ἑξῆς and τηλοῦ genitives. The frequency with which particular cases of particular nouns were used in a specifically attributive sense caused them to become, as it were, petrified, the other cases of the nouns in question passing out of use, and the original force of those that were retained being gradually forgotten. Prepositions are adverbs employed to define nouns instead of verbs and adjectives. Their appearance in the Indo-European languages is comparatively late, and the Homeric poems allow us to trace their growth in Greek. The adverb, originally intended to define the verb, came to be construed with the noun, and the government of the case with which it was construed was accordingly transferred from the verb to the noun. Thus when we read in the Odyssey(iv. 43), αὐτοὺς δ᾽ εἰσῆγον θεῖον δόμον, we see that εἰς is still an adverb, and that the accusative is governed by the verb; it is quite otherwise, however, with a line like Ἀτρείδης δὲ γέροντας ἀολλέας ἦγεν Ἀχαιῶν ἐς κλισίην (Il. i. 89) where the adverb has passed into a preposition. The same process of transformation is still going on in English, where we can say indifferently, “What are you looking at?” using “at” as an adverb, and governing the pronoun by the verb, and “At what are you looking?” where “at” has become a preposition. With the growth and increase of prepositions the need of the case-endings diminished, and in some languages the latter disappeared altogether.
Like prepositions, conjunctions also are primarily adverbs used in a demonstrative and relative sense. Hence most of the conjunctions are petrified cases of pronouns. The relation between two sentences was originally expressed by simply setting them side by side, afterwards by employing a demonstrative at the beginning of the second clause to refer to the whole preceding one. The relative pronoun can be shown to have been in the first instance a demonstrative; indeed, we can still use that in English in a relative sense. Since the demonstrative at the beginning of the second clause represented the first clause, and was consequently an attribute of the second, it had to stand in some case, and this case became a conjunction. How closely allied the adverb and the conjunction are may be seen from Greek and Latin, where ὡς or quum can be used as either the one or the other. Our own and, it may be observed, has probably the same root as the Greek locative adverb ἔτι, and originally signified “going further.”
Another form of adverb is the infinitive, the adverbial force of which appears clearly in such a phrase as “A wonderful thing to see.” Various cases, such as the locative, the dative or the instrumental, are employed in Vedic Sanskrit in the sense of the infinitive, besides the bare stem or neuter formed by the suffixes man and van. In Greek the neuter stem and the dative case were alone retained for the purpose. The first is found in infinitives like δόμεν and φέρειν (for an earlier φερε-ϝεν), the second in the infinitives in -αι. Thus the Gr. δοῦναι answers letter for letter to the Vedic dative dāvāne, “to give,” and the form ψεύδεσθαι is explained by the Vedic vayodhai, for vayās-dhai, literally “to do living,” dhai being the dative of a noun from the root dhā, “to place” or “do.” When the form ψεύδεσθαι had once come into existence, analogy was ready to create such false imitations as γράψασθαι or γραφθήσεσθαι. The Latin infinitive in -re for -se has the same origin, amare, for instance, being the dative of an old stem amas. In fieri for fierei or fiesei, from the same root as our English be, the original length of the final syllable is preserved. The suffix in -um is an accusative, like the corresponding infinitive of classical Sanskrit. This origin of the infinitive explains the Latin construction of the accusative and infinitive. When the Roman said, “Miror te ad me nihil scribere,” all that he meant at first was, “I wonder at you for writing nothing to me,” where the infinitive was merely a dative case used adverbially.