Moderator note: Questions about the l' in l'on are very common, and the topic has been discussed many times on our forums. We have merged a large number of those discussions together here. Consequently, this thread is very long, but it is also very complete. You will find many usage examples, and many comments about style and frequency of use for on/l'on. You will also find information about etymology. If you are not interested in such extensive discussion, the following FAQ may help you: Q: Why is there an l' in phrases like ce que l'on dit ("what people say") and si l'on veut ("if one wants to")? A: The easy answer is that the l' is there for "euphonic" reasons -- to make things easier to pronounce: que l'on, si l'on, où l'on, etc. are more fluid than qu'on, si on and où on. The more complicated answer is that this l' is left over from a definite article in historical French. Please see the sites below for an explanation of the etymology. Q: Can we translate the l' using the word "it"? Does it refer to something else in the sentence? Does it have a grammatical function? A: No, the l' does not mean "it." As a matter of fact, it doesn't have any meaning at all. You can simply ignore the l' when translating. It does not have a grammatical function in modern French, and it does not refer to anything else in the sentence. Q: Is it "better" to include the l'? A: The l' is often omitted in casual speech, but it is generally included in proper written French. Q: Are there rules about when you can use the l' and when you can't? A: There are guidelines. Please see the sites below. For more information: French about.com has usage guidelines The BDL article describes etymology and pronunciation information Druide has extensive explanation and guidelines More discussion in the on / l'on - L euphonique thread on the French Only forum ~~~~~~~ In school I was taught it has to be: "C'est un tunnel qu'on construisait en ..." But after speaking and writing with some natives, I could figure out that most of them would use "que l'on" in the above-mentioned sentence. The same goes for "si, et, ou and qui". I know it sounds better the way natives do it, but why was I taught incorrectly at school? Or is "l'on" colloquial? More examples: "On n'avait pas non plus toute l'expérience que l'on aurait eue aujourd'hui." That's a "self-made" sentence, but here's one of my textbook: "Le transport des passagers et celui des voitures, des cars et des camions n'y est possible que par train: par TGV ou, si on voyage en voiture, avec les trains-navettes qui traversent le tunnel en 35 minutes." Would you please tell me what's the correct term and which of them is colloquial?