Sure, but isn't that begging the question--assuming that principle parts actually exist to begin with? I'm not talking about predicting the 5th principle part from the 6th. I'm talking about predicting the perfect middle from a root and an agreement paradigm. Then φ changing to μ is nothing more than morphophonological nasalization.Stephen Carlson wrote:Usually they are, but there are a few pesky exceptions.
For γράφω, you have γέγραμμαι and ἐγράφθην, but for κόπτω, it's κέκομμαι and ἐκόπην. In one case the -μμ- corresponds to -φθη-, but in the other the -μμ- corresponds to -θη-. So the 6th PP is not predictable from the 5th; you may have to memorize the root too and have therefore not reduced what is needed to memorize.
In the other direction, take the verbs στέφω and στρέφω. Their 6th PPs are ἐστέφθην and ἐστρέφθην, respectively, but their 5th PPs are ἔστεμμαι and ἔστραμμαι, with different vowels. So the 5th PP is not predictable from the 6th PP. I don't know if memorizing the root even helps this example.
This happens at morpheme boundaries all the time.Phonological Rule wrote:[+stop] --> [+nasal] / _ [+nasal]
(Note for Randall: I'm not saying anyone should be teaching formal mophophonological rules. I'm just saying the the structure of words is constructional...just like, well, everything else)