Martin v. Löwis <report@bugs.python.org> wrote
   on Sat, 01 Oct 2011 10:59:48 -0000: 

>>  * Word characters are Alphabetic + Mn+Mc+Me + Nd + Pc.

> Where did you get that definition from? UTS#18 defines
> "<word_character>", which is Alphabetic + U+200C + U+200D
> (i.e. not including marks, but including those

From UTS#18 RL1.2A in Annex C, where a \p{word} or \w character 
is defined to be 

 \p{alpha}
 \p{gc=Mark}
 \p{digit}
 \p{gc=Connector_Punctuation}

>> I think you are looking for here are Word characters without 
>> Nd + Pc, so just Alphabetic + Mn+Mc+Me.  
>> 
>> Is that right?
> 
> With your definition of "Word character" above, yes, that's right.

It's not mine.  It's tr18's.

> Marks won't start a word, though.

That's the smarter boundary thing they talk about.  

I'm not myself familiar with \pM

> As for terminology: I think the documentation should continue to
> speak about "words" and "letters", and then define what is meant
> in this context. It's not that the Unicode consortium invented
> the term "letter", so we should use it more liberally than just
> referring to the L* categories.

I really don't think it wise to have private definitions of these.

If Letter doesn't mean L?, things get too weird.  That's why 
there are separate definitions of alphabetic, word, etc.

--tom