Original sentence: If the crystal system is trigonal, then the lattice system is exagonal unless the space group is one of the seven in the  rhombohedral lattice system consisting of the 7 trigonal space groups in the table above whose name begins with R.The Bravais lattice of the space group is determined by the lattice system together with the initial letter.of its name, which for the non-rhombohedral groups is P, I, F, or C, standing for the principal, body centered, face centered, or C-face centered lattices
Edited sentence: If the crystal system is trigonal, then the lattice system is hexagonal unless the space group is one of the seven in the  rhombohedral lattice system consisting of the 7 trigonal space groups in the table above whose name begins with R.The Bravais lattice of the space group is determined by the lattice system together with the initial letter of its name, which for the non-rhombohedral groups is P, I, F, or C, standing for the principal, body centered, face centered, or C-face centered lattices