Research in Loanword Phonology has extensively examined the adaptation processes of Anglicisms into recipient languages. In the Tijuana–San Diego border region, where English and Spanish have reciprocally existed, Anglicisms exhibit two main phonetic patterns: some structures exhibit Spanish phonetic properties, while others preserve English phonetic features. This study analyzes 131 vowel tokens drawn from spontaneous conversations with 28 bilingual speakers in Tijuana, recruited via the sociolinguistic ‘friend-of-a-friend’ approach. Specifically, it focuses on monosyllabic Anglicisms with monophthongs by examining the F1 and F2 values using Praat. The results were compared with theoretical vowel targets in English and Spanish through Euclidean distance analysis. Dispersion plots generated in R further illustrate the acoustic distribution of vowel realizations. The results reveal that some vowels closely match Spanish targets, others align with English, and several occupy intermediate acoustic spaces. Based on these patterns, the study proposes two phonetically based corpora—Phonetically Adapted Anglicisms (PAA) and Phonetically Non-Adapted Anglicisms (PNAA)—to capture the nature of Anglicisms in this contact setting. This research offers an empirically grounded basis for cross-dialectal comparison and language contact studies from a phonetically based approach.

Loanword Research on Anglicisms has largely centered on lexical borrowing and phonological adaptation with comparatively limited attention to morphosyntactic integration in recipient grammars. This study examines the morphosyntactic behavior of 74 single-word Anglicisms—monosyllabic structures with monophthongal vowels—drawn from phonetically classified corpora of spontaneous Mexican Spanish produced by Spanish–English bilinguals in the Tijuana–San Diego border region. Building on prior acoustic analyses based on F1 and F2 vowel measurements, the study investigates the relationship between phonological adaptation and morphosyntactic integration. Results reveal a gradient pattern of incorporation. Anglicisms exhibiting Spanish-like phonetic properties tend to occupy canonical syntactic positions and show greater compatibility with Spanish functional morphology, whereas phonetically non-adapted forms more frequently resist morphological marking and display island-like behavior within otherwise Spanish clauses. The analysis examines distribution across nominal, adjectival, and prepositional domains and object positions to assess morphosyntactic integration degrees. The former is illustrated as follows: (1) guardo cash ([kaʃ]) por si acaso; (2) si hacen match ([mæʧ]), puede funcionar. Adopting a usage-based and contact-oriented perspective for syntactic borrowing, the study is situated within the Matrix Language Frame model and recent approaches to insertional borrowing. A central contribution lies in establishing a principled link between morphosyntactic behavior and an independently motivated phonetic classification, offering convergent evidence for the systematic integration of Anglicisms into Spanish grammar. At a broader analytical level, the study advances debates on syntactic borrowing and contact-induced change by demonstrating that Anglicisms are subject to Spanish morphosyntactic constraints rather than functioning as unconstrained lexical insertions, and by developing an interface-based account of borrowing that captures the gradient nature of grammatical incorporation in contact settings and contributes a corpus-based, empirically grounded perspective to typologies of borrowing in Spanish contact linguistics.

Loanword Research on Anglicisms has largely centered on lexical borrowing and phonological adaptation, with comparatively limited attention to morphosyntactic integration in recipient grammars. This study examines the syntactic behavior of single-word Anglicisms in Mexican Spanish, drawing on phonetically classified corpora of 131 monosyllabic Anglicisms with mon-ophthongs extracted from spontaneous speech by Spanish–English bilinguals in the Tijuana–San Diego border region. Building on prior acoustic analyses based on F1 and F2 vowel measure-ments, the study investigates the relationship between phonological adaptation and morphosyn-tactic integration. Results reveal a gradient pattern of incorporation. Anglicisms exhibiting Span-ish-like phonetic properties tend to occupy canonical syntactic positions and show greater com-patibility with Spanish functional morphology, whereas phonetically non-adapted forms more frequently resist morphological marking and display island-like behavior within otherwise Spanish clauses. The analysis examines distribution across nominal, adjectival, and prepositional domains, as well as object positions, enabling a fine-grained assessment of degrees of morpho-syntactic integration. The former is illustrated as follows: (1) Guardo cash ([kaʃ]) por si acaso (2) Si hacen match ([mæʧ]), puede funcionar Adopting a usage-based and contact-oriented perspective for syntactic borrowing (Bybee, 2015), the study is situated within the Matrix Language Frame model (Myers-Scotton, 1993; Muysken, 2000) and recent approaches to insertional borrowing (Poplack & Dion, 2012; Onysko & Win-ter-Froemel, 2011). A central contribution lies in establishing a principled link between morpho-syntactic behavior and an independently motivated phonetic classification, offering convergent evidence for the systematic integration of Anglicisms into Spanish grammar. At a broader ana-lytical level, the study advances debates on syntactic borrowing and contact-induced change by demonstrating that Anglicisms are subject to Spanish morphosyntactic constraints rather than functioning as unconstrained lexical insertions, and by developing an interface-based account of borrowing that captures the gradient nature of grammatical incorporation in contact settings and contributes a corpus-based, empirically grounded perspective to typologies of borrowing in Spanish contact linguistics.