Is the sound /a/ considered to be an original phoneme of Proto-Indo-European? Or is it only the result of laryngeal colouring of former *e (or *o?). In the vocabularies I have seen of Indo-European, /a/ is especially frequent initially and before and after /k/ (and sometimes /g/ or /gh/ - usually the velar stops, but sometimes also the palatals). This suggests that it is a colouring of another vowel (probably *e) in the vicinity of guttural consonants, including the vanished laryngeal H2. But is there any evidence that there was an original /a/ independent of surrounding sounds? I know that postulated *a is rare in verb roots outside of initially and near /k g gh/, but if one looks at attested IE languages, one finds that /a/ seems quite frequent in Latin. What explains /a/'s frequency in Latin? Where also does Celtic (Irish, Welsh, Breton, Scots) /a/ come from (besides syllabic m and n becoming am, an)? Is it
common in these languages, or relatively infrequent, since it was relatively infrequent in PIE? The same remarks and questions apply to the diphthongs *ai and *au, which seem to be common only initially and after /k/, although in Latin ae and au are not infrequent. What explains these diphthongs' frequency in Latin?
I invite any and all to reply to my questions.
Andrew Jarrette