This book provides an original, full-scale, exploration in applying the principles and practices of Systemic-Functional Linguistics at the level of word phonology in English, German, Welsh and Tera (Nigeria). The relationship between lexicogrammar and word phonology is demonstrated, and the place of word phonology is set within the full range of a hierarchy of phonological expression. The function of phonology is given a new understanding in its relationship to lexicogrammar, and the notion of system is given extensive illustration in the numerous networks that are proposed. The special characteristic features of Systemic Phonology are compared with the theory and structures of other approaches to phonology. The choice of the four languages is deliberate: English as the most described language in the world; German as a language in the same linguistic family as English; Welsh as another Indo-European language, but from a different linguistic family; and Tera as a language with absolutely no family connection to the others. The principal units of word phonology are the foot and its equivalent in non-stress languages, the syllable, the phoneme and allophone. Allophonic variants are included, since their phonetic realization is determined by the phonology of a language, rather than on purely phonetic criteria.