As far as I can work it out, grammatical change follows phonological change,
because the phonemes tend to collide, eg:

Latin ending -us loses -s, -um loses -m, degrades to -o
All of a sudden the speakers can't distinguish between
Da caballo puero
and Da puero caballo
"Give the boy a horse",
so they start working out means and methods of making that distinction.
Syntax - word order - starts to play a more important role, and prepositions
start to take over from cases.  Da ad puero caballo - "Give to the boy a
horse", makes more sense than making an inspired guess.

Just some details I've picked up on my travels through the Romance thicket.

Wesley Parish

On Sun, 07 Sep 2003 15:06, you wrote:
> J.K.Hoffman wrote:
> > Okay, so I've got a couple of questions regarding language change.
> > What's more common, change in pronunciation of words?  Or, change in
> > grammatical structure?
> Pronounciation, by far.  Sometimes within the space of 2-3 generations.
> Grammatical change seems a lot more resistant; I think the schoolmarms have
> finally given up on "whom" and maybe "it is I" etc, but those battles were
> going on even before I was born a Long Time Ago.
> > Or, are there other ways that are more common that I'm not aware of?
> Interesting and sometimes amusing things happen in the semantic area--
> aside from words being lost, you can find pejoration, amelioration,
> loss/addition of connotations, confusion (e.g. disinterested vs.
> uninterested), not to mention all the slang that comes and goes. Groovy.
> An interesting and not overly-technical book on semantics (in the
> linguistic, not philosophical, sense) is Stephen Ullmann's; I disremember
> the title at the moment; it may be "Meaning and Change of Meaning".  Old,
> but still available.

Mau e ki, "He aha te mea nui?"
You ask, "What is the most important thing?"
Maku e ki, "He tangata, he tangata, he tangata."
I reply, "It is people, it is people, it is people."