Edward Sapir (18841939). Language: An Introduction to the Study of Speech. 1921.
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.
The simplest, at least the most economical, method of conveying some sort of grammatical notion is to juxtapose two or more words in a definite sequence without making any attempt by inherent modification of these words to establish a connection between them. Let us put down two simple English words at random, say