General Principles
"Vocabulary" and "grammar" are not hermetically sealed-off categories. If grammar describes the structure of a language, it goes without saying that no such description can be offered without constant reference to word material illustrative of various structural features. But it is also true that there can be no dictionary of words presented as amorphous raw material. Lexical listings are necessarily possessed of structure, and the structure of words and phrases is a matter of grammar.
These observations are not to suggest that the distinction between vocabulary and grammar might be abandoned, nor even that their treatment under separate heads is exclusively a matter of practical convenience. They are merely to restate the fact that the vocabulary and the grammar of a particular language are interdependent as naturally and necessarily compatible aspects of one and the same phenomenon. Beyond this they may raise the question as to what special characteristics distinguish the relationship of vocabulary and grammar in the case of a planned interlingua.
The basic character of any language is largely determined by features of a structural, i.e., a grammatical nature. Let the dictionary of a language be invaded by hordes of foreign words, as long as its patterns of word and sentence structure stay intact, the foreign material will eventually be assimilated and the basic character of the language will survive essentially unchanged.
This principle, applicable to all languages, is strikingly illustrated by English with its very considerable Romance vocabulary assimilated to a Teutonic base.
There is no apparent reason that planned auxiliary languages should be governed by fundamentally different laws. Yet superficially their situation does look completely reversed. There has been ample opportunity to observe that once agreement on the best possible vocabulary for an auxiliary language is assured, diversities of opinion in regard to grammatical problems lead to nothing more than parallel variants of one general language. But this is not so because the grammatical structure of planned languages is less significant than that of natural languages; it is so because an established vocabulary implies the settlement of so many questions of structure, i.e., of grammar, that the remaining grammatical features play of necessity a subordinate and dependent role.
It is, then, only a seeming reversal of the principle of grammar's precedence over vocabulary that after the vocabulary of a planned auxiliary language has been determined all that remains to be said by way of grammar must be completely subordinated to the structural characteristics of the vocabulary. The grammatical structure of a planned language determines its basic character precisely as does the structure of a natural language But the determination of the vocabulary leaves few grammatical questions wholly indeterminate.
The vocabulary of IALA's form of the interlingua is that embodied in the Interlingua-English Dictionary. The fundamental principle of the corresponding grammar must be that this grammar shall be the minimum or simplest possible system fit to govern the use of the chosen vocabulary in coherent speech.
IALA's endeavor to compile a dictionary of generally international words led of necessity to the assembly of a basically Romance vocabulary. The source languages to whose domain search and research could safely be restricted were Spanish and Portuguese, Italian, French, and English, with German and Russian as possible substitutes. 1
Hence a sound working principle in the elaboration of IALA's system of grammar is that the term "minimum grammar" shall not permit the suppression of any grammatical feature which according to the testimony of the source languages is indispensable in the government of their vocabularies and hence of the vocabulary of the interlingua embodied in the Interlingua-English Dictionary. In other words, every grammatical feature which is encountered in all the source languages shall be retained in the grammar of the interlingua, or negatively, no grammatical feature shall be so retained if it is missing from as much as one of the source languages. Thus, for instance, the feature of a distinctive plural form of nouns must be retained because it is found to exist in all the source languages while the feature of grammatical gender can be dispensed with because it is missing in one of the source languages, i.e., in English.
The determination of what grammatical features are to be retained in the interlingua leaves open the question of the forms which are to be used to represent them. The forms of grammatical features are determined as far as possible by means of the method worked out for the "standardization" of forms of words as analyzed in the Introduction to the Interlingua-English Dictionary.
If the material of the following grammar appears to be organized in a somewhat unorthodox way, the reason is simply that certain chapters ordinarily represented in conventional grammars could be omitted in the present instance because their subject matter is completely covered by the Dictionary. Thus the grammar contains, for example, no special discussion of prepositions and conjunctions except for a paragraph under the heading of word building. It will also be noted that there is no section concerned with problems of syntax. Such problems do exist in Interlingua, but it seemed expedient to treat them in connection with the various parts of speech whose functions in the sentence can be made to involve all syntactic questions of practical import. The technical apparatus of the Dictionary (list of abbreviations, etc.) applies to the Grammar as well and has not been included again in the following pages.
1 For further details, see Interlingua-English Dictionary, "Introduction."