Original: These six exceptions are ced/er, cess- sed/er, sess- mov/er, mot- ten/er, tent- vert/er, vers- veni/r, vent- and the verbs formed out of them using prefixes.
Simplified: These six exceptions are: ced/er, cess- sed/er, sess- mov/er, mot- ten/er, tent- vert/er, vers- veni/r, vent- and the verbs formed from them with prefixes.