You've probably seen it – that long dash, longer than a hyphen, used to add emphasis or a sudden thought. It's called an em dash, and it can sometimes leave writers scratching their heads, especially when it comes to capitalization. So, do you capitalize after an em dash?
The short answer, and the one that usually applies, is no. Think of the em dash as a way to insert an aside or a parenthetical thought within a sentence. Just like you wouldn't capitalize after a comma that sets off a clause, you generally don't capitalize after an em dash.
For instance, "She finally arrived – a little late, but with a smile – ready to begin."
Here, "a little late" is a natural continuation of the sentence, not a new one, so it stays lowercase.
However, there's a crucial exception. If the thought you're introducing after the em dash is a complete, independent sentence, then yes, you should capitalize it. This is where the em dash acts more like a period, signaling a distinct break and the start of a new idea.
Consider this: "He had one goal – to finish the marathon. He trained for months."
In this case, "to finish the marathon" is a complete sentence, so it gets a capital 'T'. The em dash here serves to dramatically separate the goal from the subsequent action.
It's a bit like the difference between a quick breath and a full stop. The em dash can do both, and its punctuation partner – capitalization – follows suit.
When in doubt, ask yourself: Is this a continuation of the existing thought, or is it a brand new, standalone sentence? That distinction is usually your best guide. Style guides, like those from Microsoft or Trinity College, often emphasize clarity and natural flow, and this rule helps achieve just that. The goal is always to make your writing as clear and easy to follow as a friendly conversation.