This picture represents the side of the lamb and provides nomenclature of the cuts.
Lamb side is divided in 4: Leg, whole loin, front, flank.
Leg is divided in 3: Shank , leg (shank portion), leg (butt portion).
Leg could be divided in 2 (leg short cut): Sirloin, leg short cut (which divided in: shank and leg (shank portion).
Whole loin is divided in 2: Loin, rib.
Front is divided in 4: Shoulder, breast, shank, neck.