The maqam consists of at least two jins, or scale segments. "Jins" in Arabic comes from the ancient Greek word "genus," meaning type. In practice, a jins (pl. ajnas) is either a trichord, a tetrachord, or a pentachord. The trichord is three notes, the tetrachord four, and the pentachord five. The maqam usually covers only one octave (two jins), but sometimes it covers more than one octave. Like the melodic minor scale and Indian ragas, some maqamat have different ajnas, and thus notes, while descending or ascending. Because of the continuous innovation of jins and because most music scholars don't agree on the existing number anyway, it's hard to give an accurate number of the jins. Nonetheless, in practice most musicians would agree on the 8 most frequently used ajnas: Rast, Bayat, Sikah, Hijaz, Saba, Kurd, Nahawand, and Ajam — and a few of the most commonly used variants of those: Nakriz, Athar Kurd, Sikah Beladi, Saba Zamzama. Mukhalif is a rare jins used exclusively in Iraq, and it does not occur in combination with other ajnas.