• 3-minute read
• 6th February 2020

Writing Tips: How to Use the Number Sign (#)

If you use social media, you probably know the “#” sign or hashtag. This symbol has several names, including the number sign, pound sign, hash sign, and octothorpe. But where does it come from? How else is it used? And how should you use it in your writing? Let’s take a look.

The History of the Number Sign

The hash sign can be traced to a Roman unit of measure, the libra pondo (or “pound weight”). This was sometimes abbreviated to the symbol “℔,” which evolved into “#” by the nineteenth century. By this point, it was widely known as a “number sign” when used before a number:

Please answer question #2.

Please answer question number two.

And in the USA, it is also known as the “pound sign.” This is because we sometimes use it to indicate an imperial pound when placed after a number:

We need 2# of beef for the pie.

We need two pounds of beef for the pie.

Outside North America, however, “hash sign” and “number sign” are more common. To abbreviate the unit of mass, countries like the UK and Australia use the abbreviation “lb” instead.

Modern Uses

Over the years, the hash sign has picked up several other uses, including:

• As a proofreading mark that indicates the need to insert a space.
• In writing music, as it looks similar to a sharp note but is easier to type.
• Inserting comments within code in various programming languages.
• As the notation “###,” which indicates the end of a press release.
• To create hashtags on various social media platforms.

This final use is probably the most common nowadays, as it allows people to quickly find posts on a specific subject or theme (e.g., #proofreading).

When to Use a Hash Sign in Your Writing

It would be unusual to need the hash or number sign in formal writing, such as an essay. However, as detailed above, this symbol has several uses in different contexts. Using the hash sign to replace the word “number” is common in less formal writing, so it is fine to use it as long as:

• You’re certain the reader will understand how you’re using it.
• It doesn’t undermine the formality of the document.

If you want to be 100% sure you’re using this symbol correctly, though, it never hurts to have your writing proofread. We have expert editors ready to help, so why not submit a document today?