Centum-satem Isogloss

Centum-satem Isogloss

The centum–satem division is one of many isoglosses of the Indo-European language family, related to the different evolution of the three dorsal consonant rows of the mainstream reconstruction of Proto-Indo-European :

The terms Centum versus Satem languages is derived from the words for the number "one hundred" in a traditional representative language of each group: Latin centum and Avestan satəm.

The centum group includes Italic, Celtic, Germanic, Hellenic and Tocharian. This group merged PIE dorso-palatals and dorso-velars but retain the labio-velars as a distinct set. Tocharian largely reflects a situation where all three PIE dorsal series as well as all voicing/aspiration distinctions (originally constituting nine separate consonants) have merged into a single phoneme /k/. This has led some writers to suggest that Tocharian does not fit the Centum–Satem model. However, some PIE labiovelars are in fact represented by a labiovelar-like element or by a non-original sequence /ku/. Along with other evidence, this suggests that labiovelars were distinct in Proto-Tocharian and only later merged with velars (as happened independently in Old Irish and to some extent in some other languages), making Tocharian a clearly Centum language.

The satem languages (which have the sibilant where the centum equivalents have the velar) include Baltic, Slavic (or Slavonian), Armenian and Indo-Iranian. This group lose the labial element of the PIE labiovelars and thus merge them with the dorso-velars while the dorso-palatals remain distinct. Balto-Slavic is largely satem but evidences centum development in some words, suggesting that "Satemization" was incomplete. There is residual evidence of various sorts in satem languages of a former distinction between velar and labiovelar consonants, indicating the earlier centum state.

Recent evidence from Luwian indicates that all three dorsal consonant rows were maintained separately in Proto-Anatolian, and the Centumization observed in Hittite only occurred after the breakup of Common Anatolian.

The isogloss only applies to the parent language with the full inventory of dorsals. Later sound changes within a specific branch of Indo-European that are analogous to one of the centum or satem changes, such as the palatalization of Latin k to s in some Romance languages or the merger of *kʷ with *k in the Goidelic languages, are excluded.