C2[C or U]the process of converting something from one thing to another: Solar power is the conversion of the sun's energy into heat and electricity.Change and changes›a process in which someone changes to a new religion or belief: Her conversion to Buddhism/Islam was a very gradual process.He used to be very right-wing, but he's undergone something of a conversion recently.Change and changes›[C]a place for living in that has been changed from its previous use: a barn/factory conversionHouses and homes