Proto-Baltic language
Proto-Baltic is the unattested, reconstructed ancestral proto-language of all Baltic languages. It is not attested in writing, but has been partly reconstructed through the comparative method by gathering the collected data on attested Baltic and other Indo-European languages. It represents the common Baltic speech that approximately was spoken between the 3rd millennium BC and ca. 5th century BC, after which it began dividing into West and East Baltic languages. Proto-Baltic is thought to have been a fusional language and is associated with the Corded Ware and Trzciniec cultures.
Generally, Proto-Baltic had a SOV word order. Proto-Baltic is said to have possessed certain unique traits, such as turning short Proto-Indo-European vowels *o, *a into *a, retaining and further developing the Proto-Indo-European ablaut, retaining *m before dental consonants, the productivity of the word stem ē and free accentuation with two pitch accents. Also, the proto-language is thought to have had its own set of diminutive suffixes, identical endings for verb tenses and moods, past tense by applying thematic vowels *-ā- and *-ē-, as well as its own lexicon, including onomastic elements.
Proto-Baltic area
Baltic hydronyms cover a vast area of 860,000 km2 from Vystula River in the west to Moscow in the east and from the Baltic Sea in the north all the way to Kyiv in the south. The current Lithuanian and Latvian lands combined constitute approximately one-sixth of the former Baltic territory. Some researchers suggest that in the past Baltic lands from Vystula to Daugava were inhabited by Baltic Finnic tribes but they were assimilated by the Baltic newcomers later on. There is still an ongoing debate regarding the boundary of hydronyms in the southwest: Lithuanian linguist believed that practically all of the basins of Oder and Vystula Rivers belonged to the Baltic hydronym habitat while German linguist Hermann Schall suggested that Baltic hydronyms could be found much further west all the way to Elbe, Saxony and Rügen island. During the 2nd and 1st millennium BC, the Baltic people inhabited larger territories than Germanic and Slavic people did at the time. It is estimated that the Proto-Baltic lands had up to 500,000 people.Inhabitants of the Proto-Baltic area were surrounded by Germanic people in the west, Slavs in the south and Finno-Ugric people in the north and northeast. Russian philologist Vladimir Toporov believes that during 1000–800 BC Proto-Germanic people began expanding into the western Baltic territory starting from the Pasłęka River. Later on, the Baltic area began shrinking even more due to the migration of the Goths. During the migration period Slavic people began expanding into the northern and eastern territories of the Balts. From 11th to 12th century, Russian scriptures mention ongoing battles near Moscow with Eastern Galindians. Since 1225, the conquests of the Teutonic Order in the current Baltic region intensified and later on resulted in the extinction of the Old Prussian speakers in the 18th century.
Relationship with other language groups
Slavic languages
After a long-running debate in the 20th century about the exact nature of the relationship between the Baltic and Slavic branches of the Indo-European family, in the 21st century many historical linguists moved firmly in favour of a shared genealogical history between these two branches, both deriving from a common intermediate source, Proto-Balto-Slavic, after the breakup of Proto-Indo-European. Those in opposition continue to be sceptical about the nature of such a relationship and are uncertain whether it is even ascertainable. While Balto-Slavic has been traditionally divided into two main branches, viz. Baltic and Slavic, some linguists like Frederik Kortlandt or Rick Derksen proposed that Proto-Balto-Slavic split into three language groups — East Baltic, West Baltic and Proto-Slavic — without a Proto-Baltic stage, which is a view opposed by Miguel Villanueva Svensson and Eugen Hill. Historical linguist Brian D. Joseph argues that in the context of other Indo-European phylogenetic clades, the qualitative evidence for Balto-Slavic is not on par with Indo-Iranian, insofar as Balto-Slavic lacks evidence for shared culture. Other scholars point out that the phonology and morphology, which is shared by all known Baltic languages, is much more archaic than that of Proto-Slavic, retaining many features attributed to other attested Indo-European languages roughly 3000 years ago.It is also known that some Baltic and Slavic languages have more in common than others: Old Prussian and Latvian share more commonalities with Slavic languages than Lithuanian does. Some similarities between Baltic and Slavic can be found on all levels of linguistic analysis, which led German philologist August Schleicher to believe that there was indeed a common point of development. French linguist Antoine Meillet, however, rejected this idea and claimed that similarities between Baltic and Slavic languages were a result of close contact. Meanwhile, Latvian linguist Jānis Endzelīns suggested that following the split of PIE, Baltic and Slavic languages evolved independently, but later experienced a common period of greater contact. Jan Michał Rozwadowski proposed that the two language groups were indeed a unity after the division of Indo-European, but also suggested that after the two had divided into separate entities, they had posterior contact. Russian linguists Vladimir Toporov and Vyacheslav Ivanov believed that Proto-Slavic language formed from the peripheral-type Baltic dialects. Thus, there are at least six points of view on the relationships between the Baltic and Slavic languages.
Germanic languages
There is some vocabulary that Baltic and Germanic languages share, excluding loanwords. Common vocabulary mostly includes words relating to work, equipment, agriculture etc., such as Proto-Baltic *darbas, meaning 'work' and Proto-Germanic *derbaz, meaning 'bold, determined, strong' < *derbaną 'to work', Proto-Baltic *derṷā and Proto-Germanic *terwą, meaning 'tar, resin', Proto-Baltic *gāmurii̯as and Proto-Germanic *gōmô, meaning 'palate'. Baltic and Germanic languages also share numeral formation for 11 to 19, both partially possess the same formation of verbs in past tense, absence of the aorist. According to German linguist, at first Proto-Baltic was a centum language along with Proto-Germanic, but it eventually became satem later on. Some scholars believe that Baltic and Germanic contacts are older than those with Slavic languages while others claim the opposite. According to Lithuanian linguist, Germanic people borrowed certain suffixes from their Baltic neighbours, such as *-ing-, *-isko-, *-ō-men-. Both Baltic and Germanic emotional verbs possess similar semantic development, which is evinced by roots like *dhers- and *dreǵh-. This semantic group is also noted for having exclusive isoglosses, though they differ in meaning.suggested that in the 3rd millennium BC Germanic and Baltic languages shared a common phase of linguistic convergence and that Baltic dialects were initially closer to the Germanic dialects than Slavic ones. He noted that although Germanic languages possess more lexical commonalities with Slavic languages, Baltic and Germanic groups share a greater number of grammatical innovations. This is evinced by the possession of *-mo-, second consanguineous component, identical dual number pronouns in first and second person, common grammatical constructions to describe natural phenomenons and resemblance of comparative degree prefixe -esnis to its corresponding Germanic counterpart.
Finnic languages
The linguistic influences of Baltic Finnic languages, which are associated with the eastern Baltic area, can be observed in certain grammatical innovations, such as the merger of some cases with postpositions, thus forming new additional cases : inessive *šakāi + en > *šakāi̯en 'in the branch', illative *šakān + nā > *šakānā 'into the branch', adessive *šakāi + prei > *šakāipei ' by the branch' and allative *šakās + prei > *šakāspei ' to the branch'. The impact of the Finnic languages over Baltic languages also explains the widespread use of a non-agreed modifier expressed by the genitive of a noun in contrast to other Indo-European languages that usually apply an agreed modifier expressed by an adjective as well as the usage of indirect mood when one is retelling an event without knowing whether it actually happened.In turn, Baltic Finnic languages have many borrowings from the Baltic languages. Baltic languages accelerated diphthongization in these languages, the impact of the Baltic languages explains compound forms of the past tense, development of the agreed modifier not found in other Uralic languages, 'of the big city', 'towards the big city; for the big city', fortifying suffix -pa / -pä also, etc.
Phonetics and phonology
Vowels and diphthongs
The vowels of Proto-Baltic changed little in comparison to PIE: short vowels *a and *o coincided into a single *a while the reduced Indo-European vowel schwa primum also turned into *a as it did in other Indo-European languages of Europe and it ceased to exist in the middle of words. According to the proponents of the Laryngeal theory, the schwa primum appeared by turning laryngeals into vowels, which makes its reconstruction for PIE unnecessary and obsolete. There were four short and five long vowels as well as four short and six long diphthongs as presented below:Vowels *a, *e, *i, *u together with sonorants *r, *l, *m, *n of Proto-Baltic were used to form mixed diphthongs as they are being used in the modern Baltic languages today. It is also well known that there were mixed diphthongs with long vowels at the endings. Long diphthongs can be reconstructed when glottaling, compared to PIE, the position of stress in the example is conditioned by Hirt's law. Long mixed diphthongs, which position in the morpheme is hardly determined or their existence is questionable are presented in Italic: