The word in English (as in all Indo-European languages) may or may not have a constituent structure, so that its unity may be simple or complex. Affixes are added on to roots and bases in derived words, complicating the structure. The constituent parts of the word are all ultimately subordinated to the unity of the whole, and the process of word formation may be accompanied by phonetic alternations of the base or root.

Thus, for instance, a word like penitentiary is the product of penitent + –iary, and comports the change of stem-final /t/ to /∫/, yielding the pronunciation /ˌpɛnɪˈtɛnʃəri/. This change is called PALATALIZATION because the dental stop of the deriving base is replaced by the palatal fricative in the derived form. The change is part of the regular alternation in English derivational morphology (but not only) between the consonants /t d s z/, on the one hand, and /∫ tʃ ʒ /, on the other, before the front vowel /i/ or the glide /j/; hence consent ~ consensual, tort ~ tortuous, grade ~ gradual, process ~ processual, Paris ~ Parisian, use ~ usury, seize ~ seizure, etc. The derived form is marked in comparison to the unmarked deriving base, hence the appearance of the marked sound /∫/ in place of the unmarked /t/, etc.. The alternation of stem-final consonants is a sign of the hierarchical relation between the two forms (quite apart from the presence of the suffix in the derived form).

It should be noted that American and British usage in the forms at issue is not always the same. Before the suffix {-ian], for instance, the British form does not palatalize the stem-final consonant, hence Christian is /ˈkrɪstjən/ in British English but /ˈkrɪstʃən/ in American; and Parisian in Brit. /pəˈrɪzɪən/ as contrasted with U. S. /pəˈriʒ(ə)n/. This also applies to non-derived words like prescient, for which Brit. is /ˈprɛsɪənt/ but U. S. /ˈprɛʃ(i)ənt/; cf. fustian Brit. /ˈfʌstɪən/ but U. S. /ˈfʌstʃən/, etc.

Linguists have, for the most part, not understood the function of phonetic alternation outside a purely segmental (linear) phonetic context, but it is clear from the examples cited here that palatalization contributes to the structural unity of the word and is thereby SEMIOTICALLY significant. The word as a structural unit always tends to subordinate its parts to itself as a whole, and in the case of derivational morphology (including word formation) the deriving base’s being altered in its stem-final consonant in the process of derivation is a sign that the base has been rendered subordinate in the context of a derived form.

A useful check on this analysis can be seen in the process of what is called UNIVERBATION, where two or more words are contracted into, or treated as, one. In the case of palatalization across morpheme boundaries within the word, the process described above applies without fail, whereas across word boundaries (where there is no pause) it may apply optionally, as in the phrase this year pronounced frequently in American English with [ʃ] instead of [s] for the last consonant of this (cf. gotcha /ˈgɒtʃə/ for got you).