Root allomorphy depends on head movement: Support from Breton pluralization

The trigger of allomorphy should be sufficiently local to the morpheme subject to the allomorphy. Bobaljik adopts as a working hypothesis that this locality should be defined as head incorporation: a head that conditions root allomorphy must be in the same complex head as the root. As such, he captures the fact that comparative suppletion is blocked in periphrastic comparatives. This snippet shows that Breton plurality provides further empirical support for the hypothesis that the appropriate locality condition for allomorphy is head incorporation. Breton plurals may show a vowel modification in the stem. In other words, the stem may be subject to allomorphy.