Eugene Oh wrote:
> Hmm this is most interesting. In fact, this is the first time that I
> have heard of there being separate imperatives for different "aspects"
> in Ancient Greek, or for that matter in any language. 

This applies to Russian and AFAIK to all the Slav languages, as well as 
to modern Greek. Indeed, ancient Greek also had a third set of 
imperative for the perfect aspect (not the same as perfective); but 
these were far less common. The modern Greek language distinguishes, as 
do the Slav languages, only between imperfective & perfective as, I 
understand, do the Semitic languages.

> Or perhaps I
> have and it is only the suppletion in this case that is fascinating me
> so, but I digress. (What is internal temporal consistency, actually?
> The term flies over my head.)

I was quoting Larry Trask's definition. I need to think about this one 
before replying. Maybe one of our professional linguists on the list can 
explain better than I can.

> So we've got Εἶπε, Μνημοσύνη in Ancient Greek, which then leads me to
> my next question -- what is the cognate, if there is one, of εἶπε(ιν?)
> in other IE languages?

It developed from a reduplicated strong aorist form *wewep-. The stem 
*wep-, found also in the noun _epos_ or _wepos_ (the form with initial 
digamma is attested) "word", is derived from PIE *wek_w- ~ wok_w-, cf. 
Latin _uocare_.

Entia non sunt multiplicanda
praeter necessitudinem.