Semicolons are stronger and heavier than commas, and as such, they create a slightly longer or more significant pause. The semicolon joins two independent clauses, usually on the same topic or thought. I frequently use them to join two independent clauses that are already joined by a conjunction, when I want the longer pause of a semi plus the aural smoothness of a conjunction; I have always thought this was technically wrong, but the rule list linked above assured me that this is acceptable so long as there is a comma in the first independent clause. (And considering the length of the sentences I write, there usually is!) These examples are apparently both correct:
Serendipitously, the squid surfed into sight at that second; startled, it squirted away.If you are making a list in which the list items themselves contain commas, then the list items should be divided by semicolons as follows:
Serendipitously, the squid surfed into sight at that second; but Sir Septimus screamed, and it squirted away.
The squid ate five sardines; six mussels, which he found rather hard to open; seven anemones, sans clownfish; and a Boston cream pie.Perhaps because they're used in so much eighteenth- and nineteenth-century English literature, I often think of semicolons as a little bit formal or fussy; they're the maiden aunt of punctuation, as opposed to the boldness of a dash or the unobtrusiveness of a comma. But like many maiden aunts, they are wonderfully useful at keeping many unruly things in line, be they ideas, clauses, or commas. Indeed, because they're so good at neatly delineating multiple similar items within a sentence, I also feel like semicolons signal complexity; when used correctly, their presence in your prose says that you know how to present and manage all these items competing for the reader's attention -- that you have things under control.
Finally, Semikolon is an excellent German paper-goods company, should you be a stationery hound like I am.