# Should “So”, “Therefore”, “Hence”, and “Thus” be followed by commas?

Often, I have come across sentences that begin with "So". Should such an usage of "So" be followed by a comma?

Are the following examples correct.

1. He is very good at computers. So, I think he can fix your computer.

2. When we multiply an even number with another even number, the result is an even number. So, the square of an even number is an even number.

What happens if we choose to use "Therefore", "Hence", or "Thus" instead of "So"? Do the rules still remain the same?

1. When we multiply an even number with another even number, the result is an even number. Therefore, the square of an even number is an even number.

2. When we multiply an even number with another even number, the result is an even number. Hence, the square of an even number is an even number.

3. When we multiply an even number with another even number, the result is an even number. Thus, the square of an even number is an even number.

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On the use of commas, and on punctuation in general, I recommend, as I have before, this guide written by Larry Trask. – Barrie England Feb 23 '12 at 15:58
There is a "rule" that says that, like And and But, So should never begin a sentence. But people do it all the time. And that's fine. So don't worry about it. – slim Feb 23 '12 at 16:09
@slim: So, we'll take that as implicit support for not adding a comma after "so", then? – FumbleFingers Feb 23 '12 at 16:48
@BarrieEngland Indeed. Trask was a superlative linguist and a tireless and skilled explainer. – John Lawler Feb 23 '12 at 18:29
@BarrieEngland Can you summarize the answer to the OPs particular question (about a comma after an initial entry word) in your answer? Otherwise, this doesn't say anything other than give a reference. – Mitch Feb 23 '12 at 18:59

The short answer is "no." The longer answer is: a comma is not a requirement but neither is it something to avoid.

What may blow your mind is that the comma is not required anywhere in any of your examples. It is a matter of style.

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Commas are not determined by grammar or by which words they follow. Comma indicates a particular intonation. If you would use that intonation in speaking the sentence, use a comma; if not, don't. So it's important to hear what you're writing, in your mind if nowhere else.

Generally in short sentences you wouldn't, but if the sentence following the introductory word is long, you might well. Also generally speaking, if the material coming first is long (as it is in this sentence but wasn't in the previous sentence), you would.

Punctuation is not absolute; it's a work in progress.

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I think in OP's context, including the comma reflects a certain degree of "hesitant attention-grabbing" - often typical of some people's conversational style within a group. It causes the "So" to linger longer before the "follow-up" conclusion - implicitly there's a pause there that means something like (please start listening to me now because I'm about to say something relevant to what's just been said) – FumbleFingers Feb 23 '12 at 16:56
That's certainly one recognizable usage. There are lots of others, along with myriads of individual styles, not all useful. As I said, a work in progress. – John Lawler Feb 23 '12 at 18:28
Haha - it'll be a lifetime's work, I think! But I certainly think your point about "Generally in short sentences you wouldn't" covers many situations. Conversely, I find it hard to imagine anyone saying, for example, "It's raining, so, here's an umbrella". – FumbleFingers Feb 23 '12 at 20:19

The trend is away from commas, and I use them where they help make the sentence easier to read, or help the flow. More important is consistency. If the comma is omitted in one place, it should be omitted in all instances thereafter. Useful punctuation is invisible; the reader shouldn't notice it.

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