I do a lot of my writing in a restaurant, so I’m a little bit sympathetic with the restaurant staff in this Bent Pinky comic, but the punch line brings up a little-used but useful technique in good writing, a semicolon. (Shall I drift onto another of my Greek rabbit trails? The punctuation used by Greeks for their question mark looks like a semicolon.)
Maybe people don’t use it because the rules for semicolon usage are vague. Look at it this way: if the rules are vague, you can get away with using it, and no one will complain, because they don’t know either!
Okay, start with commas. Use a comma when the part after the comma depends on what’s before the comma. Look at any sentence in this post for examples. (Yes, we have other uses for commas, but those are for another post.)
Then there’s the period. You know how to use those. Two sentences can be on the same topic, but they stand alone.
Semicolons stand between these two. Technically the material on each side of a semicolon can stand alone (both sides have to have a subject and predicate) but they share a dependency of meaning that ties them closely together. Not enough for a comma, but too dependent for a period. I ran into this on Facebook. (If the owner identifies him-or herself, I’ll be happy to give credit.) It’s a good example of when a semicolon should have been used instead of that comma:
See how a semicolon would have been a better break? That’s not so hard; go thou and do likewise.