The adjectival noun /digu/ 'unripe, raw' has a form /-rigu-/ (or occasionally /-rugu-/ when used as a compound initial, where it means 'unripe, raw, unconscious, dead', as in /-rigu=rabi-/ 'to fall down unconscious/dead' with /=rabi-/ 'to fall down'. The form /-rigu-/ is subject to Hardening P-18 after stop or nasal, giving /-digu-/ but even in such cases the representation must be /-rigu-/ at one stage to prevent application of ngu-Epenthesis P-1.
Other d/r alternations are accounted for by Hardening P-18 and by Lenition P-16. However, the present d/r alternation has a quite different distribution. It is independent of the choice of preceding segment and so is distinct from Hardening P-18 (which, however, may apply to the output). It also differs from Lenition P-16 in that the presence or absence of another derivational or compounding element before the stem is not relevant; both noun /digu/ and compound initial /-rigu-/ typically occur directly after the inflectional prefix (noun-class or pronominal). Moreover, the noun /digu/ is attested as compound final in /mada-ngu-digu/ 'raw (green) grass' with /mada/ 'grass', retaining its stop /d/ (and thus requiring ngu-Epenthesis P-1).
| (P-17) | digu-Lenition |
| d → r // -__ | |
| only in the stem /digu/ 'raw' when used as a compound initial |