the outwardly parallel one of goose and geese.  It remains true that there is (or was) an inherent tendency in English, at the time such forms as geese came into being, for the utilization of vocalic change as a significant linguistic method.  Failing the precedent set by such already existing types of vocalic alternation as sing—­sang—­sung, it is highly doubtful if the detailed conditions that brought about the evolution of forms like teeth and geese from tooth and goose would have been potent enough to allow the native linguistic feeling to win through to an acceptance of these new types of plural formation as psychologically possible.  This feeling for form as such, freely expanding along predetermined lines and greatly inhibited in certain directions by the lack of controlling types of patterning, should be more clearly understood than it seems to be.  A general survey of many diverse types of languages is needed to give us the proper perspective on this point.  We saw in the preceding chapter that every language has an inner phonetic system of definite pattern.  We now learn that it has also a definite feeling for patterning on the level of grammatical formation.  Both of these submerged and powerfully controlling impulses to definite form operate as such, regardless of the need for expressing particular concepts or of giving consistent external shape to particular groups of concepts.  It goes without saying that these impulses can find realization only in concrete functional expression.  We must say something to be able to say it in a certain manner.

Let us now take up a little more systematically, however briefly, the various grammatical processes that linguistic research has established.  They may be grouped into six main types:  word order; composition; affixation, including the use of prefixes, suffixes, and infixes; internal modification of the radical or grammatical element, whether this affects a vowel or a consonant; reduplication; and accentual differences, whether dynamic (stress) or tonal (pitch).  There are also special quantitative processes, like vocalic lengthening or shortening and consonantal doubling, but these may be looked upon as particular sub-types of the process of internal modification.  Possibly still other formal types exist, but they are not likely to be of importance in a general survey.  It is important to bear in mind that a linguistic phenomenon cannot be looked upon as illustrating a definite “process” unless it has an inherent functional value.  The consonantal change in English, for instance, of book-s and bag-s (s in the former, z in the latter) is of no functional significance.  It is a purely external, mechanical change induced by the presence of a preceding voiceless consonant, k, in the former case, of a voiced consonant, g, in the latter.  This mechanical alternation is objectively the same as that between the noun house and the verb to house.  In the latter case, however, it has an important grammatical function, that of transforming a noun into a verb.  The two alternations belong, then, to entirely different psychological categories.  Only the latter is a true illustration of consonantal modification as a grammatical process.