The Irish bouzouki, although not strictly a member of the mandolin family, bears a reasonable resemblance, and also has a similar range, to the octave mandolin. It was derived from the Greek bouzouki (a long-necked lute), constructed like a flat-backed mandolin and uses fifth-based tunings, most often G2–D3–A3–D4. Other tunings include: A2–D3–A3–D4, G2–D3–A3–E4 (an octave below the mandolin—in which case it essentially functions as an octave mandolin), G2–D3–G3–D4 or A2–D3–A3–E4. Although the Irish bouzouki's bass course pairs are most often tuned in unison, on some instruments one of each pair is replaced with a lighter string and tuned in octaves, similar to the 12-string guitar. While occupying the same range as the octave mandolin/octave mandola, the Irish bouzouki is theoretically distinguished from the former instrument by its longer scale length, typically from , although scales as long as , which is the usual Greek bouzouki scale, are not unknown. In modern usage, however, the terms "octave mandolin" and "Irish bouzouki" are often used interchangeably to refer to the same instrument.