No so-so use of so

My husband is a math guy. His grammar has improved in the nearly two decades we’ve been together, but ultimately, he’s brilliant with numbers. So when his co-workers ask him grammar questions, he happily suggests their questions for columns. That’s how this column came about: “How do you use so? I really like the word, and I use it a lot, so I need to know what I’m doing.”

The word so functions in a variety of ways. Unlike most of the other coordinating conjunctions, sohas several definitions that make using it correctly somewhat complicated. Normally, a coordinating conjunction takes a comma when connecting two independent clauses (clauses that can stand alone as complete sentences):

Marty ate beans, so he got gas.

So works in this case when it means, “therefore,” or “consequently.”  When used to mean, “in order that,” so often does not require a comma because it turns the second clause into a subordinate (dependent) clause:

James took some medicine so he wouldn’t get gas.

In case you’re thinking this is a bit too complicated to remember, you’re in luck: There’s a trick.  In the second case, when so means, “in order that,” it is often followed by that. If you can follow your so with that, you don’t need the comma because instead of functioning as a coordinating conjunction, in this case, so is a subordinating conjunction. Is your head spinning?

That’s not the only exception to so, though. Other coordinating conjunctions are rarely, if ever, followed by a comma. The reason for this is simple: Conjunctions connect, and commas divide.  Commas often come before the conjunctions, but they rarely follow them. This rule is especially true at the beginning of sentences, where people are prone to beginning with and orbut (something that should be done only very sparingly and with purpose) and then following those conjunctions with a comma. Those people are almost always wrong.

Strangely, though, the rules change a bit with so.

Unlike and andbut, so is often used in informal speech as both verbal filler and as a way to start a new line of conversation. In this second instance – and please note it should be reserved for very informal, conversational writing and speaking – the so should be followed by a comma:

So, has Marty tried Beano yet?

There are a number of other so rules, but they’re not as widespread in misuse as the ones listed. I guess they’re only so-so.