The Satem division of the Indo-European family includes the following branches: Indo-Iranian, Baltic and Slavic, Armenian, Albanian, perhaps also a number of barely documented extinct languages, such as Phrygian and Thracian (see: Indo-European languages). All those languages show the characteristic change of the so-called Proto-Indo-European palato-velars (*k^, *g^, *g^h) into affricate and fricative consonants articulated in the front of the mouth. For example, *k^ became Sanskrit s′, Avestan, Russian and Armenian s, Lithuanian s^, Albanian th, etc. At the same time, the protolanguage velars (*k, *g, *gh) and labio-velars (*kw, *gw, *gwh) merged in the Satem group, the latter losing their accompanying lip-rounding.
By contrast, in the remainder of the Indo-European family (the then-called Centum languages), palato-velars lost their palatal component and merged with plain velars, while labio-velars remained distinct.
The Satem shift is conveniently illustrated with the word for '100', Proto-Indo-European *k^mtom, which became e.g. Avestan satem (hence the name of the group), Lithuanian s^imtas, Russian sto, etc., as contrasted with Latin centum (pron. [kentum]), English hund(red)- (with /h/ from earlier *k, see Grimm's law), Greek (he)katon, Welsh cant, etc.
The Satem group is a paraphyletic group and thus not a phylogenetic unit.
