Is it online, on line or on-line?

Although all forms are seen in written communications, only two forms are correct (on line and on-line); the difference between them (ie the use of the hyphen) is very important and applies to many other grammatical forms.

To say that you are ‘online’ would be like saying that a tennis player is ‘oncourt’ or that a builder is ‘onsite’, rather than saying she/he is ‘on site’. We will never see the back of ‘online’, however, and the overall situation may change. To remain consistent though…

  • Where the phrase is just a factual statement, we use two words.
  • Where the entire phrase is used to further describe something else, we must use the hyphen to show this.

Examples:

  • My PC is now on line, so you can use it.
  • This is an on-line transaction.

This solution is then perfectly consistent with all other forms in this grouping:

  • My car is now on site.
  • This is an on-site car park.