Un vs l’un

Which one?

Do you know the difference between un and l’un? If you answered, "Huh? Why would you ever put the definite article l’ in front of un?" then this is the lesson for you. There are two reasons to use l’ in front of un: one has to do with register, the other with euphony.

First things first: the word un has three potential roles:

  1. indefinite article (a, an)
  2. indefinite pronoun (one)
  3. number (one)

When un is an article or a number, it’s always un: it cannot be replaced with l’un. So how do you know which role it’s playing? If un is followed by a noun, it’s either a number or an article. If it’s followed by anything else, such as the preposition de, it’s a pronoun, and may potentially be replaced with l’un.

Once you’ve determined that un is a pronoun, there are two reasons you might want to change it to l’un.

1) Formality

L’un is more formal than un, so using it makes your French sound more elegant.

Par exemple…

Vous devrez passer l’un de nos examens.   You’ll have to take one of our tests.
J’espère assister à l’une de vos conférences.   I hope to attend one of your conferences.

2) Euphony

At the beginning of a sentence or clause, it’s customary (though not required) to use l’un rather than un, because l’un just sounds better there. (see also on vs l’on)

Par exemple…

L’un de mes enfants est en retard.   One of my kids is late.
Oh là là, l’une d’entre elles a manqué le bus.   Oh dear, one of them missed the bus.

 If the pronoun is plural, the definite article has to be plural as well: les uns, les unes. This is most commonly found paired with les autres; for example,

Les uns parlent, les autres écoutent.   Some talk, others listen.

Fixed expressions with l’un

  • c’est tout l’un tout l’autre – there’s no grey area, the situation is black and white
  • de deux choses l’une – there are two possibilities
  • l’un à l’autre – to each other
  • l’un après l’autre – one after the other
  • l’un dans l’autre – all in all
  • l’un d’eux, l’un d’entre eux, l’une d’elles, l’une d’entre elles – one of them
  • l’un et l’autre – both of them
  • l’un l’autre – one another, each other
  • l’un ou l’autre – either one, one or the other
  • ni l’un ni l’autre – neither one
  • soit l’un soit l’autre – either one, one or the other

 In fixed expressions, l’un is required. Elsewhere, it’s optional – you can decide whether to use it to make your French more formal or euphonic.

 Incidentally, l’Un is the French equivalent of "The One" from the philosophical discipline of henology.

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Un vs l'un - French lesson

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