I just searched quickly how to explain that the semi-colon is somehow half a colon. I couldn't find anything.
Although, confusingly, I believe the English semicolon functions more similarly to the punctuation associated with a Greek/Latin colon.
I'd like to add that it is wrong to think about commas, semi-colons, etc. in terms of duration of a pause in the speech. These signs articulate written sentences' syntax, and it sometimes relate to pauses when read aloud, but it is not a bijection. When analysing recordings, J. Drillon (Traité de la ponctuation française) showed that the correlation is really weak.
Leads to some interesting PHP errors, like: Parse error: syntax error, unexpected T_PAAMAYIM_NEKUDOTAYIM
Of course, that may be cause it's exactly the same in my native italian.