What evidence links Baltic-Finnic languages with Sami languages?

The Baltic-Finnic and Sami languages are recognized as being closely related within the Finno-Ugric group, a connection often referred to as North Finnic. While they are not considered to be as closely related as members within the Baltic-Finnic group itself, they share several significant linguistic links:1

• Grammatical Structure: The grammars of Sami languages are similar to those of Finnish, reflecting their shared heritage within the Uralic family.2
• Consonant Gradation: Both groups exhibit consonant gradation, an alternation of consonants based on syllable structure. Although the specific processes differ—with the Baltic-Finnic type representing a more plausible phonetic change—the similarities suggest an areal relationship. Evidence indicates that early Sami may have acquired this feature through Baltic-Finnic influence.3
• Phonological Preservation: While the Baltic-Finnic languages are noted for a more conservative vowel system, the Sami languages are recognized for having best preserved the original consonant contrasts of the early Uralic language.4

Despite these shared features, the two groups remain distinct, and the syntax of Sami has been notably influenced by Scandinavian languages.2