Lesson RF4.3 question

I can't get what does "l" mean in the following phrase: Avez-vous un numéro de téléphone où *l*’on peut vous joindre? Can anyone help me with it?

Hi there Well, you will be delighted to know that "l'" means...nothing! It is called "euphony"...to make it sound better. This "l" should not be confused with the "l" pronoun as in "je l'ai vu". Here: téléphone où l'on peut vous joindre it's to avoid the clash of "ou on". Sometimes, we see also "que l'on" instead of "qu'on", a lot harsher" Does it make sense?

[quo]*Quote:* it's to avoid the clash of "ou on".[/quo] So, do I have to use "l" here, or is optional and used in fluent speech only?

Hi there, Yes, it is definitely optional and just to "sound better". Sometimes you can even start a sentence with "l'on a vu.... (literary style) :D