Reconstruction of the Proto-Indo-European labial stops (made with the lips) and dental stops (made with the tip of the tongue touching the teeth) is fairly straightforward. More controversial is the reconstruction of the Proto-Indo-European sounds underlying the correspondences shown in Table 2.
According to the most generally accepted hypothesis, there were in Proto-Indo-European at least two distinct series of velar (or "guttural") consonants: simple velars (or palatals), symbolized as *k, *g, and *gh, and labiovelars, symbolized as *kw, *gw, and *gwh. The labiovelars may be thought of as velar stops articulated with simultaneous lip-rounding. In one group of languages, the labial component is assumed to have been lost, and in another group the velar component; it is only in the Latin reflex of the voiceless *kw that both labiality and velarity are retained (compare Latin quis from *kwi-). It is notable that the languages that have a velar for the Proto-Indo-European labiovelar stops (e.g., Sanskrit and Slavic) have a sibilant or palatal sound (s or ś) for the Proto-Indo-European simple velars. Earlier scholars attached great significance to this fact and thought that it represented a fundamental division of the Indo-European family into a western and an eastern group. The western group-comprising Celtic, Germanic, Italic, and Greek-is commonly referred to as the centum group; the eastern group-comprising Sanskrit, Iranian, Slavic, and others-is called the satem (satəm) group. (The words centum and satem come from Latin and Iranian, respectively, and mean "hundred." They exemplify, with their initial consonant, the two different treatments of the Proto-Indo-European simple velars.) Nowadays less importance is attached to the centum-satem distinction. But it is still generally held that in an early period of Indo-European, there was a sound law operative in the dialect or dialects from which Sanskrit, Iranian, Slavic and the other so-called satem languages developed that had the effect of palatalizing the original Proto-Indo-European velars and eventually converting them to sibilants.
LINGUISTICS | Non-Western traditions | Greek and Roman antiquity | The European Middle Ages | The Renaissance | Development of the comparative method | Inner and outer form | Structural linguistics in Europe | Structural linguistics in America | Transformational-generative grammar |