How to say "difference" in Arabic

Root פ-ר-ק/ف-ر-ق means 'to split apart, separate' across Semitic (compare Aramaic פרק, Akkadian parāqu). Hebrew פרק kept the concrete 'take apart, dismantle' sense and extended it to 'chapter' — a text broken into separate sections. Arabic farq stayed abstract: the 'separation' between two things, i.e. the difference. This is why a book chapter is called פרק in Hebrew.