froti

One root, frot-, and no seam anywhere in it. That is the whole morphological story, so the page is about what the verb does instead.

Froti is transitive and takes the surface, not the cleaning agent: you rub the stain, using soap. The instrument goes in with per. Two derived forms earn their keep. Frotado is the rubbing as an activity, the thing that wears a rope through. Froti sin is to rub oneself, and with the reflexive it is what the cat in the third example is doing to your leg, which is why the accusative sian kapon matters there: the cat is rubbing its own head, not somebody else's.

Do not reach for it for polishing. English "rub" covers a lot of ground and Esperanto splits it. Froti is the plain mechanical action of surface against surface. Poluri is to polish. Viŝi is to wipe, which is what you do to a table with a cloth and no pressure. Skrapi is to scrape. The one that catches learners is viŝi against froti: you viŝas the tears from a face and you frotas the mark off a shirt, and swapping them makes you sound either violent or ineffective.