My Grammar and I (Or Should That Be 'Me'?): Old-School Ways to Sharpen Your English

C
HARLES
D
ICKENS
, A Christmas Carol
Now  fighting  a  losing  battle  against  the  less  elegant  dash  (see
here
 ),  the
semicolon  connects  two  or  more  independent  clauses  that  don’t  quite  justify
being sentences in their own right. It often replaces and or but . It may be helpful
to think of it as a ‘supercomma’.
I have tickets for Wimbledon
tomorrow. I bet it rains.
These two short sentences
read a bit jerkily.
I have tickets for Wimbledon tomorrow
but I bet it rains.
A little clumsy.
I have tickets for Wimbledon
tomorrow; I bet it rains.
Much better!
Rule 1: You must have a finite clause sentence (see
here
) on both sides of the
semicolon.
Rule  2:  Semicolons  are  followed  by  a  lower-case  letter,  unless  the  word  in
question is a proper noun.

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A  semicolon  is  also  used  instead  of  a  comma  to  break  up  items  in  a  long  and
complicated list, particularly when the list has plenty of commas in it already, as
in the Dickens quote above.