Semicolon
A 
semicolon is a 
punctuation mark.  It is used to join two sentences slightly more closely than they would be joined if separated by a 
full stop (or 
period).  The semicolon is also used as a sort of "senior comma" to make meaning clear in a sentence where 
commass are already being used for other purposes.
Examples:
-  I am alone; my wife had to leave.
-  I traveled to London, England; Tijuana, Mexico; and Reykjavik, Iceland.
-  Lisa scored 2,845,770 points; Marcia, 2,312,860; and Jeff, 1,726,640.
In 
computer programming, the 
semicolon corresponds to 
Unicode and 
ASCII character 59, or 
0x003B.