Re: [tied] PIE Word Formation (2)

>
>The tendency to use contrastive accent must have operated throughout the
>history of PIE and into the early "dialectal" stages. Several
>chronological layers can be discerned. To begin with the oldest, there
>was a time when accent retraction to a formerly unaccented syllable
>caused the appearance of a full vowel there, while the syllable that had
>lost its accent was phonetically reduced. In particular, thematic *-o-
>became *-u-. Let us imagine a root like *kret- (a real example, with the
>approximate meaning of 'strengthen'. The addition of anaccented
>adjectival suffix like *-r�- forms a verbal adjective: *krt-r�-
>'strengthened', dissimilated to *krt-�-. Accent retraction produces the
>noun *kr�t-u-s 'being strong, power'. Note that the full vowel is
>inserted where it belongs, which means that at that stage speakers were
>aware of the underlying vocalism of the root: perhaps the actual
>realisation of the weak grade at that time was *kr&t-, with an
>appreciable (even if reduced) vowel. Later an adjective was formed from
>*kr�t-u- by another application of the principle of contrastive accent,
>this time yielding *kr.t-�- (at a time when a stressed zero grade was
>already possible, but loss of accent still caused vowel reduction).
>
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Is this the origin of all (or most) u-stem adjectives and nouns?  Does the presence of *-u- in adjectives always or usually imply that the adjective at one stage had the suffix *-ro-?  And are such adjectives (and nouns) sufficiently distinguished semantically from original *-o- adjectives (and nouns), assuming these remained (i.e. is it necessary to have a contrast between *-us and *-os?)?

Andrew Jarrette