Conversion is when someone wrongfully uses property of another for their own purposes or alters or destroys it. In an action for conversion, the taking of the property may be lawful, but the retaining of the property is unlawful. To succeed in the action, the plaintiff must prove that he or she demanded the property returned and the defendant refused to do so.
Conversion is a modern form of the old-fashioned action called trover. Damages may be recovered for the replacement value of the property as well as for the loss of its use. Conversion is very similar to theft, but is a civil action, not a criminal action.