This is the 6526th most frequent Russian word.
citroën
The word "Citroën" is not Russian; it is a French automobile brand.
Here, 'Citroën' is used as a proper noun referring to a specific brand and object – a car that the speaker has purchased.
Я купил новый Citroën и он просто великолепен.
I bought a new Citroën and it's just marvelous.
In this context, 'Citroën' is used as a proper noun to describe the brand for categorization of products.
Среди всех автомобилей Citroën мне нравится модель C4.
Among all Citroën cars, I like the model C4.
Here, 'Citroën' serves as a proper noun referring to the speaker's specific car.