A correspondent writes to ask for an explanation of prosiopesis and whether this can be used in relation to writing.
The term was introduced by Otto Jesperson in his Philosophy of Grammar. Here's his definition: 'the speaker begins to articulate, or thinks he begins to articulate, but produces no audible sound (either for want of expiration, or because he does not put his vocal chords in the right position) till one or two syllables after the beginning of what he intended to say'. He gives the example of 'Morning' for 'Good morning'. Another example would be 'Kyu' for 'Thank you'.
This is plainly a phonetic definition, and it could only apply to writing in cases where the same type of communicative pressure applies. I suppose one could adapt the definition as follows: 'the writer begins to type, or thinks he begins to type, but produces no graphic form (either for want of energy, or because he does not put his fimgers in the right position) till one or two syllables after the beginning of what he intended to type'.
I do this often, when typing on screen, but you don't see the results in print because typing allows revision in a way that speech does not. However, in styles of writing which simulate spontaneous speech, I think we can see the same sort of process in operation. Looking back over some instant messaging logs, for example, I can see several examples. My daughter sent me one the other day which began 'Morning'. And any genre of spontaneous written electronic communication (chat, social networking, twitter, etc) is likely to display such things.
The notion becomes more obviously applicable to writing if we replace Jesperson's phonetic definition by one in terms of syntactic or semantic processing. When someone says 'Coming out tonight?' or 'Looks like rain', these days people talk more in syntactic terms, such as 'elision', 'pro-drop', and suchlike.