Code-switching beyond phases

This study examines the syntactic structure of Urdu–English code-switching (CS) through a lens of Phase Theory, focusing on parametric variation between two languages. Recognizing CS as a vibrate domain of contact language, this analysis assumes that bilingual syntax is governed by the universal computational principles. Employing a mixed-method research design, this study gathers naturalistic data from balanced Urdu–English bilinguals. Findings reveal frequent use of phase heads—That in English and keh in Urdu—as well as light verbs kar and ho, each showing distinct preferences in bilingual context. The Urdu complementizer keh introduces embedded clauses irrespective of clausal mood and notably does not project a specifier position. Moreover, verbal phase heads are categorized into agentive and stative types based on argument structure. These light verbs are selected not by tense phrase (TP), but by the aspect head Asp, which intervenes between the vP and TP. In Urdu–English CS, light verbs are embedded within a layered structure comprising voice, aspect and tense—each computing language-specific features independently. The findings support Phase Theory, affirming that syntactic derivation precedes in discrete, hierarchical phases, validating a universal bilingual architecture.