Indefinite pronouns refer to people or things without saying exactly who or what they are. "N'importe qui" is part of the indefinite pronouns.
How to use the indefinite pronoun n'importe qui in French
Look at these sentences:
N'importe qui peut entrer chez toi.Anyone can get into your house.
Elle fait confiance à n'importe qui.She trusts anyone.
Juliette et Marie parlent à n'importe qui.Juliette and Marie talk to anyone.
Note that "n'importe qui" literally means "no matter who", and is used in French to say "anyone".
You use it ONLY in affirmative sentences to emphasise that the identity of the person referred to doesn't matter (ANY one).
You would use quelqu'un to express 'anyone' in a question.
Il y a quelqu'un ici ?Is there anyone here?
(See also Quelqu'un/Quelqu'un d'autre = Someone/Someone else (French Indefinite Pronouns))
You would use personne in a negative sentence.
Non, il n'y a personne.No, there isn't anyone.
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