When Should You Use LUn Instead of Un in French

When should you use lun and when should you use un? Whats the difference? Well, there are good reasons for this syntactical variation. Remember, French is rich in syntax, so what might seem like a minor difference in structure can translate into a major difference in sound or meaning. The difference between the two forms is fairly simple; it has to do with grammar and register, or the level of formality or informality of the surrounding language. 'L'Un' as a Pronoun In formal French, when un functions a pronoun, rather than an article or number, it can be replaced by lun. How do you know whether  un  is a pronoun, article, or number? Very simple: Any time  un  is followed by a preposition, usually  de, or by anything else other than a noun, its a pronoun. Otherwise,  un  is either a number (one) or an article (a, an).Tu dois choisir lun de ces livresYou have to choose one of these booksJai vu lun de ses amisI saw one of his friends 'L'Un'at the Beginning of a Sentence When un is a pronoun at the beginning of a sentence, it is nearly always replaced by lun, for reasons of euphony, or making pronunciation in this musical language as fluid and harmonious as possible.Lun de mes meilleurs à ©tudiants est à   lhà ´pital.One of my best students is in the hospital.Lun de vous doit maider.One of you has to help me. Expressions With 'L'Un' There are also a number of fixed expressions with lun. Cest tout lun tout lautre. Theres no in-between; everything is black and white.de deux choses lune   two possibilitieslun à   lautre     to each otherlun aprà ¨s lautre     one after the otherlun dans lautre     all in alllun deux, lun dentre eux, lune delles, lune dentre elles     one of themlun et lautre     both (of them)lun lautre     one another, each otherlun ou lautre     either one, one or the otherni lun ni lautre     neither onesoit lun soit lautre     either one, one or the other 'Un' as a Number or an Article When un is a number (one) or an article (a, an), it should not be replaced by lun.   Ã‚  Ã‚  Jai un frà ¨re et deux soeurs.I have one brother and two sisters.   Ã‚  Ã‚  Je vois une femme.I see a woman.      Cest un Apollon.Hes an Adonis.      Un jour, à §a sera possible.One day, that will be possible.      Il est dun drà ´le !Hes so funny!