英语语法：127 How Many Spaces After A Period?（在线收听）

Grammar Girl here.

This week I have two topics for you: The number of spaces after a period at the end of a sentence, and whether you should use "who" or "that" to refer to people (and pets).

Now here's our first listener question.

<His friends believe it is antiquated to use two spaces after a period at the end of a sentence.>

Yes, the caller is correct and he's also right that a lot of people haven't heard about the change.

Two Spaces After a Period -- The Old Way

Here's the deal: Most typewriter fonts are what are called monospaced fonts. That means every character takes up the same amount of space. An "i" takes up as much space as an "m," for example. When using a monospaced font, where everything is the same width, it makes sense to type two spaces after a period at the end of a sentence to create a visual break. For that reason, people who learned to type on a typewriter were taught to put two spaces after a period at the end of a sentence.

One Space After a Period - The New Way

But when you're typing on a computer, most fonts are proportional fonts, which means that characters are different widths. An "i" is more narrow than an "m," for example, and putting extra space between sentences doesn't do anything to improve readability.

Notice how in this example, the "i's" and "t" take up much less space in the proportional font than they do in the monospaced font.
Although how many spaces you use is ultimately a style choice, using one space is by far the most widely accepted and logical style. The Chicago Manual of Style (1), the AP Stylebook (2), and the Modern Language Association (3) all recommend using one space after a period at the end of a sentence. Furthermore, page designers have written in begging me to encourage people to use one space because if you send them a document with two spaces after the periods, they have to go in and take all the extra spaces out.

I know it's a hard habit to break if you were trained to use two spaces, but if you can, give one space a try.

"That" Versus "Who"

On to the next topic, @Ranix at Twitter asked me whether a dog is a who or a that. For example, should he write

A dog who wants your love...

or

A dog that wants your love...

First, let's talk very briefly about people. You can use the word "that" to refer to people, but "who" is the better choice (4).

She's the girl who teaches us grammar.
He's the boy who spilled lasagna last week.

(For more information on "who" versus "that" for people, see Grammar Girl episode #24.)

Now, on to pets. Bryan Garner from Garner's Modern American Usage says "that" and "which" are the appropriate pronouns to use for anything non-human, but that makes me wonder if he's ever had a dog.

I can't imagine referring to my dog as anything other than "who." My fish could be a "that," but my dog? She's definitely a "who." Perhaps someone else's dog could be a "that"--the dog that tore up my lawn--for example. But my dog is the dog who snuggles up to me at night.

The AP Stylebook seems to use similar logic when it comes to personal pronouns and pets. For example, they state that it's OK to call an unidentified animal "it" or "that."

Earlier, we reported on a cat that was stuck in a tree.

But they note that once the animal has a name, it merits a "he" or "she." (5)

The firefighters rescued Fluffy from the tree. She rewarded them with a boisterous meow.

I believe it's a style choice, and I recommend "who" for pets who feel like part of the family, and "that" for animals that don't.

You'll find a full transcript of this podcast at quickanddirtytips.com, along with a bunch of other great Quick and Dirty podcasts. I'm Mignon Fogarty, author of the New York Times bestseller, Grammar Girl's Quick and Dirty Tips for Better Writing, and you can find me at Twitter and Facebook under the username GrammarGirl.

That's all. Thanks for listening.