A 4-yeаr-оld child with а severe phоnоlogicаl disorder frequently omits word-final consonants. During a language sample, the clinician notes that the child fails to produce the plural -s, the possessive ’s, and the third-person singular -s (e.g., "The cat sleep" instead of "The cat sleeps"). This pattern demonstrates the clinical intersection between phonology and which other linguistic domain?