Em dash—

The em dash is this line.

—

It’s longer than an en dash, which itself is longer than a hyphen.

The em dash is a writer’s favourite.

It’s used to insert a pause between two ideas.

If you imagine a comma is a slight pause, and a full stop is a large pause, the em dash would sit between the two.

Check out how this sentence slightly changes when you use different punctuation.

Full stop

“It's OK to have occasional long sentences. They play well with both short and medium sentences to bring musicality to the copy.”

Em dash

“It's OK to have occasional long sentences—they play well with both short and medium sentences to bring musicality to the copy.”

Comma

“It's OK to have occasional long sentences, they play well with both short and medium sentences to bring musicality to the copy.”

All 3 sentences work grammatically. None are wrong. It just depends how much of a pause you want to leave between the ideas.

People with impaired vision use screen readers to read text. But the screen readers don’t deal with em dashes very well.

Instead I rely on my trusty punctuation pals:

• the full stop
• the comma