I remember my third grade days of learning how to type on a computer with my classmates. We hovered our fingers over the keyboards, wanting to scratch the back of our hands with the rough towels draping over them but didn’t in fear of not being able to blindly lock our fingers back in place.

“Sit up straight,” instructed the librarian. “Now all together, type asdfg space space hjkl.”

We typed each letter in slow, choral unison, smacking the space bar twice with our thumbs.

This was how I was taught to type, with two spaces between sentences. Or between unpronounceable letter-jumbles.

And this was how I always typed, during high school, college, grad school, and all employment positions in between.

So when I learned at my internship that I was to type with one space between sentences, I was taken aback. Has the formula changed, or was I unaware that it changed long ago?

This is where the history lesson comes in.

During the 1700s and 1800s, the spacing rule in typography was to use two spaces between sentences. Many accuse early typographers of laziness, but using two spaces was done for the opposite reason. Early typographers were very concerned about tightening or loosening a line that was both visually appealing and fit the needed letters, and using two spaces between sentences achieved the desired outcome.

Around the early 20th century, typographers switched to using one space between sentences. It was cost-effective and more efficient to use one space between sentences, and publishers quickly adapted to the change.

Then the typewriter came along. Typewriters used monospaced font, meaning that every letter is the same width and height. In other words, a lowercase L was the same size as a capital W. Monospaced font was easier to read when two spaces were between sentences, so the old way was new again.

And now the argument begins.

We don’t use typewriters anymore. Word processing programs on computers have a plethora of fonts, most of which aren’t monospaced. The standard fonts in academia or business are fonts like Times New Roman, Arial, Cambria, and Georgia–all that don’t require two spaces between sentences. Typewriter font is a thing of the past.

Or is it?

For my grad school assignments, I was required to type my assignments in Courier font (I later used Courier New to save ink). Courier font was designed to replicate typewriter font, and because typewriters use monospaced font, two spaces between sentences was easier to read.

This font requirement was implemented because it was a monospaced font. Because each letter is the same size, professors could easily guess the number of words per page (which, for me, was about 260 words per page).

In short, the professors could see if students reached the required word count on the assignment.

Towards the end of my program, I rolled my eyes when someone in my writing group turned in a fourteen-page story in Times New Roman but grumbled about my eighteen-page story in Courier New (because, if his story was in Courier New, it would have easily been five pages longer).

The recent change back to one space between sentences is because we have socially changed the fonts we use to communicate.

Why then did I learn how to type with two spaces, when I wasn’t learning to type on a typewriter?

Because my instructor learned how to type on a typewriter. And those that created typing books and computer programs also learned on a typewriter, so it was natural to continue teaching students two spaces between sentences.

So what is the correct answer? One space or two?

The answer depends on the typing situation. Use one space between sentences in documents for professional typesetters, designers, desktop publishers, and everyone else passionate about typography and fonts. Two spaces between sentences are required for some research paper formats and typewriter typing, and can also make appearances in casual letters and emails.

When in doubt, ask yourself these questions:

Am I using monospaced or proportional font?

Who is receiving this typed document? What are their spacing preferences or requirements?

As I type this blog post, I am practicing using my space bar once between sentences in hopes that I’ll remember this practice for typing content at my internship.

Do you prefer one space or two spaces between sentences? Vote here!