The relative clause in French

In English the relative pronoun (who, which etc) can vary according to whether it refers to a person or an inanimate object. This is not usually the case in French.
In French, the relative pronoun varies according to its grammatical function in the relative clause - as subject, object, possessor or agent in the relative clause.

French has one set of simple relative pronouns, and one fuller set of more specific pronouns.

The simple relative pronouns are used whenever possible.

	Subject	Object	Possessor	After common prepositions
	qui	que	dont	qui (quoi)

The more specific relative pronouns are used when it is necessary to refer back to one out of several potential antecedents in order to avoid ambiguity: they are also generally used in relative clauses with an inanimate antecedent, introduced by a preposition.

	Subject/object	Posessor	with à	After prepositions
m.sing	lequel	duquel	auquel	prep + lequel
f.sing	laquelle	de laquelle	à laquelle	prep + laquelle
m.pl	lesquels	desquels	auxquels	prep + lesquels
f.pl	lesquelles	desquelles	auxquelles	prep + lesquelles

► Relative pronouns after prepositions.
With human antecedents , the preposition is normally followed by the simple relative pronoun qui
With inanimate (non-human) anticedents the preposition is normally followed by one of the more specific relative pronouns lequel, laquelle etc.

Normally a relative clause must directly follow its antecedent, i.e. the word or group of words which it qualifies. When this is the case, it is customary to use a simple relative pronoun, in function of the syntax of the sentence.

Examples with simple relative pronouns:
►Subject and object:
    I live in a flat which is rather noisy.  
        J'habite dans un appartement qui est assez bruyant.  
    I know the lady who wrote that book:  
        Je connais la dame qui a écrit ce livre.
    Here's the money that I owe you:  
        Voici l'argent que je vous dois.
    The guy that you're looking at is my brother:  
        Le type que vous regardez est mon frère.
    The museum that we visited yesterday was very interesting
        Le musée que nous avons visité hier était très intéressant.

►Possession
(This includes real possession and other cases when English would use "of whom / of which).
    The man whose car was stolen is very angry.  
        L'homme dont la voiture a été volé est très en colère..  
    The book, whose title I forget, was very well-known in its time.  
        Le livre, dont j'oublie le titre, a été très bien connu en son temps.
    There are three people over there, two of whom I recognise.  
        Il y a trois personnes là-bas, dont je reconnais deux.
    I have two suggestions, the first of which is this.  
        J'ai deux propositions, dont voici la première..        

►Relative clauses introduced by prepositions.
    The man to whom you were talking is my father.  
        L'homme à qui vous parliez est mon père..  
    I don't know what you're thinking of.  
        Je ne sais pas à quoi vous pensez.
    He told me the name of the person he was working for.  
        Il m'a dit le nom de la personne pour qui il travaillait
    This is Pierre, a consultant without whom we'd be completely lost.  
        Voici Pierre, un consultant sans qui nous serions complètement perdus.

Relative clauses introduced by prepositions
As illustrated above, when a relative clauses with a human antecedent is introduced by a preposition, it is customary to use the simple relative pronoun qui .
It is also sometimes possible to use the short form - in this case quoi , when the relative clause has an inanimate antecedent; but this is not very common.
 
Normally when a relative clause is introduced by a preposition, and refers to an inanimate (non-human) antecedent, it is normal to use one of the more specific relative pronouns lequel,  laquelle, lesquels or lesquelles, or one of their derived forms.

Examples:
►Relative clauses introduced by prepositions, and inanimate antecedents
    The box in which I was putting them has disappeared.  
        La boîte dans laquelle je les mettais a disparu..  
    Where's the bridge under which we parked the car?  
        Où est le pont sous lequel nous avons garé la voiture?.
    He told me the name of the company he was working for.  
        Il m'a dit le nom de la société pour laquelle il travaillait
    These are tools without which we'd be completely lost.  
        Voici des outils sans lesquels nous serions complètement perdus
    Those are precisely the pictures I was referring to.  
        Ce sont précisément les images auxquelles je me référais.

Ambiguity can be caused when a relative clause has more than one potential antecedent: take this example in English:
      This is a photo of the son of my brother, who is fifteen years old.
In this example, is it the son who is 15 or the brother?  In strict grammatical terms, it must be the brother - the direct antecedent of who - but logic suggests that it is more likely to be the son.

In French, this sort of ambiguity can often (though not always) be avoided by using one of the more specific relative pronouns lequel,  laquelle, lesquels or lesquelles, or one of their derived forms, which must agree in gender and number with its antecedent.
    Thus unless two potential antecedents have the same gender and number (as in the example above, where brother and son are both masculine singular), using a gramatically specific relative pronoun can avoid ambiguity.

Examples:
►Avoiding ambiguity
    This is the daughter of my brother, whom I was talking to you about (ambiguous).  
        Voici la fille de mon frère, dont je vous parlais. (ambiguous).       
        Voici la fille de mon frère, de laquelle je vous parlais. (unambiguous).
In the second version above, laquelle can only refer to fille, not frère

   There's a lock on each drawer, which is difficult to open (ambiguous).  
        Il y a une serrure sur chaque tiroir, qui est difficile à ouvrir (ambiguous).
        Il y a une serrure sur chaque tiroir, laquelle est difficile à ouvrir (unambiguous).
In the second version above, laquelle can only refer to serrure, (n.f.) not tiroir (n.m.)
   

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