I've been learning English for 5 years, but I don't understand when or how to use underline character (_) in English.
Please can you help me explain it to me?

Example about hyphen, I read here and then I understood it. But underline I can't.

  • I don't understand how to use it in Russian. Are there any specific rules? I thought one just uses it when they feel like it. – CowperKettle Mar 25 '16 at 4:11
  • Are you sure? Maybe underline have another meaning in English. :) – DinhNguyen Mar 25 '16 at 4:17
  • 2
    The underscore character usually substitutes for the space character in cases where the latter one just can’t be used. – Violette Mar 25 '16 at 6:07

An underline is a way of emphasizing or distinguishing words from others within a sentence. Italics are another way of doing so. This article may help you out, so could this one.

To quote from one of the links: To underscore something in a piece of writing that is particularly important: “books are not to be placed on the floor.” The underline gives the word a bit more gravity. When spoken, the words "are not" would be stressed or emphasized over the other words in the sentence.

I can't figure out how to underline here, but "are not" should be underlined, though italics lends a similar emphasis.

You would use it similarly to when you might stress a word in a sentence because it is more important.

For the underscore however, it iss primarily used in programming in places which a space is not allowed (or inconvenient, like a file name). It's origin is the typewriter, where it was used to underline words, see here

  • I'm sorry, my question isn't clearly. this underline is one character, It is same as hyphen character, it isn't underline same as "This article" of you. Example: instead of I write "The name", I'll write "The_name". :) – DinhNguyen Mar 25 '16 at 4:26
  • That would be the underscore character, my apologies for not seeing that. – fyrepenguin Mar 25 '16 at 4:28
  • What is the difference between the meaning of underline and underscore? At this time, I think they have same meaning. :) – DinhNguyen Mar 25 '16 at 4:38
  • 1
    An underscore isn't generally used other than for creating blank spaces like this: ______, or in an email address where you want a space but can't put one, such as joe_smith@example.com. An underline is used to emphasize a word or words like italics would. If you've ever noticed while you speak, you might say a word louder than others in a sentence because it is more important. An underline is the visual representation of an emphasized word or phrase. – fyrepenguin Mar 25 '16 at 4:42
  • Oh, I don't see editing from your post. Thank u so much about your answer. – DinhNguyen Mar 25 '16 at 4:44

The underline (or underscore—the two terms mean the same thing) is not used as a separate character in ordinary written English. It is only used beneath characters to indicate emphasis. That's why it's called an underline.

In programming contexts, however, it is often used to replace an orthographic space, as in variable and function names, or your example:


This is because most programming languages treat an actual space as the separator between tokens, so you can't have spaces inside a name. For instance, if you have two functions named 'Print Now' and 'Print Later', your compiler will interpret these as commands to 'Print' the (probably non-existent) entities 'Now' and 'Later'.

Consequently, programmers often use the underscore character so the two parts of the name are bound together for the compiler but separated for the human reader: 'Print_Now' and 'Print_Later'.

"Camel case" is another device for accomplishing the same thing: 'PrintNow' and 'PrintLater'.

  • (y), Maybe you are programmer. In case, I understand why we use _ for functions name. :D – DinhNguyen Mar 25 '16 at 11:28

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.