All constructions which enclose more than one-unit-length construction, but no others, may be said to have the next higher (second order) constructional domain. In many languages, this may be the domain of compound words. We may now proceed to those constructions which occasionally enclose constructions of the second-order domain. For simplicity, we might take certain sequences comprising English 'N⁴' as covering a third-order domain, since some of the constructions enclosed in such a sequence may be of the second order: 'that old bookworm'. Note that not every construction enclosed within 'N⁴' is of the second order: 'that' is not, nor is 'old' (although 'old' can be replaced by one which is, as in 'that sour-faced bookworm'). None of the constructions in a particular 'N⁴' ( 'that old fellow') need be of the second order; but the fact that several of them can be replaced by second-order constructions ('that old bookworm') makes it desirable to consider 'N⁴' even then as being of the third order. [...] As we establish the constructions of some particular order, we define them in each case as possible sequences of constructions of lower orders. Thus, for English, the first-order word construction was defined as containing one member of 'N' or 'V' or 'A', etc., with or without certain accompanying bound classes. The second-order compound word was defined as containing two or more words plus the '— ' ' — contour. The third-order phrase constructions could be very roughly defined in terms of words and compound words: e.g. the noun phrase would usually contain 'T D A N', where each class and each partial sequence of classes can be repeated with a member of '&' before the second occurrence; any 'D', 'A', or 'N' could be a compound word. This procedure may be repeated until we find no larger construction or domain, in any utterance no matter how long, wich we can describe as a regular combination of the last previously established domain.
- Harris (1951), a pag.331