The lattice system is described by three basis vectors. In the rhombohedral system, the crystal is described by vectors of equal length. The rhombohedral system can be thought of as a cubic system which has a formula. a = b = c; α = β = γ ≠ 90°.
"Rhombohedral crystal system" is an ambiguous term that confuses the trigonal crystal system with the rhombohedral lattice system and may mean either of them.