Which Baltic languages share important features with Slavic languages?

The Baltic and Slavic languages share more linguistic features than any other branches of the Indo-European languages, a relationship often attributed to their development from a common ancestor or a long period of mutual contact.12

Lithuanian and Latvian, the two surviving Baltic languages, share several archaic features with Slavic languages that are not found in Old Prussian. For example, Lithuanian and Latvian share specific genitive singular endings with Common Slavic, whereas Old Prussian exhibits different inflectional patterns.1

Commonalities between Baltic and Slavic include:
* Phonology: Similarities in stress patterns and tonal correspondences, such as those between Lithuanian and Serbo-Croatian.1
* Morphology: Shared features like the genitive plural form and specific inflectional developments.1
* Syntax: Both groups use the genitive case instead of the accusative with verbs expressing negation.1
* Vocabulary: More than 100 lexical items are common to both groups in form and meaning, such as terms for "linden tree" and "horn".1

While Old Prussian differs from Lithuanian and Latvian in certain archaic features, it shares other similarities with Slavic, such as specific possessive pronoun forms.1