Canapé vs. sofa vs. divan

In France, the terms 'canapé', 'sofa', and 'divan' are used to describe various types of long upholstered furniture designed for several people to sit. While these words can sometimes be used interchangeably, they originally have different connotations and design features.

Canapé

A term often used in contemporary French to refer to a sofa, with no specific differentiation on form or function. It is commonly used in current language for any couch-like piece of furniture designed for sitting.
J'ai acheté un canapé d'angle pour mon salon.
(I bought a corner sofa for my living room.)
Ce canapé trois places est très confortable.
(This three-seater sofa is very comfortable.)

Sofa

'Sofa' is of English origin and less frequently used in French. When it is used, it often denotes a stylish or designer couch, sometimes implying a more modern or sophisticated aesthetic.
Le sofa en cuir noir donne une touche moderne à la pièce.
(The black leather sofa gives a modern touch to the room.)
Nous avons un petit sofa dans le bureau pour se détendre.
(We have a small sofa in the office for relaxing.)

Divan

'Divan' refers to a type of couch without a back or partially without a back. It can also imply furniture that is more oriental in style or adapted from historical Ottoman lounges.
Elle s'est allongée sur le divan pour lire.
(She laid down on the divan to read.)
Le divan du psychanalyste est souvent représenté dans les films.
(The analyst's couch is often depicted in movies.)

Summary

Although 'canapé', 'sofa', and 'divan' may be used by French speakers to refer to similar pieces of furniture ideal for seating, they convey slightly different images: 'canapé' is the most widely used today with no specific definition; 'sofa' suggests a stylish, more contemporary design; while 'divan' typically alludes to a backless couch or one that draws inspiration from oriental or historical styles.