How do linguists distinguish borrowed words from inherited related words in Sino-Tibetan languages?

Linguists distinguish between inherited related words and borrowed words in Sino-Tibetan languages primarily by applying the comparative method, which focuses on identifying consistent phonological correspondences within shared vocabulary.12

To differentiate these, scholars prioritize the following criteria:

• Phonetic vs. Semantic Precision: As established by linguist Paul Benedict, researchers should favor perfect phonetic correspondences—even when semantic equivalences are only close—over perfect semantic matches that lack clear phonetic evidence.1
• Basic Vocabulary: Inherited relationships are most reliably identified through core, basic vocabulary rather than cultural terms, which are more susceptible to borrowing and diffusion.13
• Structural Analysis: Because typological similarities (such as word order or simple morphology) can arise from long-term contact in linguistic areas, they are often less reliable indicators of genetic relationship than systematic sound laws.2
• Protolanguage Reconstruction: By reconstructing features of common ancestral languages, linguists can better determine if shared traits are the result of inheritance from a Proto-Sino-Tibetan source or later interaction between contiguous groups.134