Cydrywiaeth, n. homogeneity
Cydsain, n. a consonant
Cydseinio, v. to agree in sound
Cydsiarad, n. confabulation
Cydsisial, v. to whisper together
Cydsoriant, n. mutual offence
Cydsylweddiad, consubstantiation
Cydsylltiad, n. conjunction
Cydsyniad, n. unanimity
Cydsynio, v. to consent