Cîl, a recess. Cilvach, a small recess.
Clawdd, a hedge, dyke. Clawdd Offa, Offa’s dyke.
Clogwyn, a precipice.
Côch, red.
Coed, trees. Sing. coeden, a tree.
Côr, a circle, a choir. Bangor, high choir.
Corlan, a sheepfold.
Cors, a bog, or fen.
Craig, a rock, a crag. Pl. creigiau.
Croes, a cross.