A chaise longue / chaise lounge (american) has a very low or no back at all see www.distinctivechesterfields.co.uk/shop/browse_ranges/chaise_longue.html for details
Divan.........A long upholstered seat typically with a back and arms.
[Turkish, from Arabic uffa, carpet, divan, from Aramaic ipp, absolute form of ippt, mat; see pp in Semitic roots.]
Try divan.
divan
A backless sofa is called a chaise lounge. It typically resembles a sofa, but has no back, and only one arm.
Chaise Longue (Europe) / Chaise Lounge (USA)
ottoman
stool
A sofa is an English word.
In French, "sofa" is a masculine word. The article "le" is used before sofa.
The plural word for sofa is sofas.
A backless slipper is called a mule.
Backless was created in 1978-11.
The word "sofa" is derived from the Arabic word "ṣuffa," which referred to a raised seating platform with cushions. This term was adopted into various European languages before becoming "sofa" in English.