This article provides a formal phonological analysis of s-retraction, the process by which /s/ is realized as [ʃ] in /stɹ/ and /stj/ clusters, e.g. street [ʃʧɹiːt]. While previous research has focused on the sociophonetic and acoustic aspects of this phenomenon, this study situates s-retraction within Element Theory (ET), demonstrating that it is driven by the affrication of the following coronal stop. The analysis shows that both the rhotic /ɹ/ and the glide /j/ function as palatal triggers, as they both contain the palatal element |I|, which spreads leftward, affecting the coronal stop and, subsequently, the preceding /s/.
The study also explains why s-retraction is restricted to /stɹ/ and /stj/ clusters, while being absent in /spɹ/ and /skɹ/. This absence is attributed to elemental antagonism, as labials and velars contain |U|, which prevents affrication. The article further accounts for dialectal variation in yod coalescence and yod dropping, showing that the presence of these processes determines whether affrication – and, consequently, s-retraction – occurs.
Crucially, the evidence from external sandhi suggests that s-retraction is an active phonological process, rather than a purely phonetic effect. The findings align with broader cross-linguistic palatalization patterns, supporting the view that s-retraction is governed by systematic phonological principles.