Re: elision

Traditionally, slashes are used for phonemic transcription, while
square brackets are used for phonetic transcription.  See
http://en.wikipedia.org/wiki/Phoneme.  Basically, variations in
pronunciation that don't affect meaning are said to be phonetic; those
that do affect meaning are phonemic.

The difference in English between [b] and [p] is phonemic, because
"bat" and "pat" are two different words.  But the difference between
[p] and [p_h] isn't, because it's wholly predictable (initial p's get
aspirated, other p's don't) and because aspiration doesn't affect the
"sound" heard by a monolingual native English speaker.

For instance, if I say the word "pot", it comes out something like
[p_hA?].  The p is aspirated, the vowel is more like an [A] than an
[O], and the t turns into a glottal stop.  That doesn't change the
fact that the underlying phonemic sequence is /pOt/, since everyone
would understand the same word if I actually said [pOt] with no
aspiration, "British" vowel, and carefully articulated [t].

Another way of looking at it: when you're talking about how something
comes out in actual speech, use square brackets.  Use slashes when
you're talking about idealized Platonic pronunciations.