Languages of the Indo-European family are classified as either centum languages or satem languages according to how the dorsal consonants (sounds of “K”, “G” and “Y” type) of the reconstructed Proto-Indo-European language (PIE) developed. An example of the different developments is provided by the words for “hundred” found in the early attested Indo-European languages (which is where the two branches get their names). In centum languages, they typically began with a /k/ sound (Latin centum was pronounced with initial /k/), but in satem languages, they often began with /s/ (the example satem comes from the Avestan language of Zoroastrian scripture).
The satem languages belong to the Eastern sub-families, especially Indo-Iranian and Balto-Slavic (but not Tocharian), with Indo-Iranian being the major Asian branch and Balto-Slavic the major European branch of the satem group. It lost the labial element of Proto-Indo-European labiovelars and merged them with plain velars, but the palatovelars remained distinct and typically came to be realised as sibilants.[7] That set of developments, particularly the assibilation of palatovelars, is referred to as satemisation.
