This is the 9861st most frequent French word.
faux
False; fake.
Here, 'faux' is used as a noun to refer to something that is not genuine, a counterfeit or forgery.
Ce tableau est un faux.
This painting is a fake.
In this sentence, 'faux' functions as an adjective to describe the gemstone as not real or authentic.
Elle portait une pierre précieuse faux dans son collier.
She wore a fake gemstone in her necklace.
'Faux' here is used as an adjective to imply that the smile is not genuine or heartfelt.