kanapo

Two words, one piece of furniture. Sofo sits at rank 1,304 and kanapo here at rank 2,361, and in ordinary use they are interchangeable: both are the long padded seat in the living room. If you want a distinction, the one PIV suggests is roughly the English settee-versus-divan one - a kanapo has a back and arms, a sofo is the more general soft couch - but nobody will correct you, and most speakers simply use whichever came to them first. Write either, recognise both.

The seam is fake, and it is a good one. Esperanto has a productive suffix -uj- and a root kano (a reed or cane), so a learner meeting kanapo cold may reasonably try kan- plus something. It does not work: there is no suffix -ap- in the language, and the couch has nothing to do with reeds. Kanapo is a single indivisible root, kanap-, and it has to be learnt whole.

Worse, it has a near-neighbour. Kanabo is hemp, and it differs from kanapo by one voiced consonant in the middle. Say them apart deliberately when you are learning them, because in the x-system they are one keystroke apart and a typo produces a real word rather than an obvious error.

What the root can do. Kanapeto is a small couch, kanapa describes anything belonging to it, and sur la kanapo is where the evening happens. The furniture around it - a seĝo, a table, a lamp - fills the salono, which is the drawing room or sitting room the couch is normally in.