in law, unauthorized possession of personal property causing curtailment of the owner's possession or alteration of the property. The essence of conversion is not benefit to the wrongful taker but detriment to the rightful owner.

Conversion concerns possession, not ownership; thus, unauthorized taking of an object from a renter is the same as if the renter were owner. The property must be personal—as opposed to land—but may be merely a paper (e.g., a club membership card) entitling the possessor to something.

To be conversion, a taking of property must be without the owner's consent. There must be some act giving the taker some control over the object, though actual physical removal is not essential.

The taking need not be malicious or even knowledgeable. Thus, one can commit conversion unaware of the owner's claim—although sometimes the owner must give notice of ownership (when a taker might believe the item has been abandoned). If the owner's mistaken belief that the object is not his causes a wrongful taking, however, that taking is not conversion.

Besides ordinary unauthorized takings, certain exceptional situations constitute conversion: detention of goods under an invalid contract; obtaining goods by fraud or duress; sale of another's property, if delivered; taking of specific money (e.g., in a lost wallet).

Legal remedies for conversion used to be a tangle of formalities under the common law, but modern statutes have greatly simplified these. Generally the remedies for conversion allow return of the object taken and compensation for deprivation of its use, interest that would have been earned by the monetary value of the object and the cost of seeking its return (not including attorney's fees).

in syllogistic, or traditional, logic, interchanging the subject and predicate of a categorical proposition (q.v.), or statement. Conversion yields an equivalent proposition (and is hence a valid inference) in general only with so-called E and I propositions (universal negatives and particular affirmatives). For example, the converse of the E proposition “No men are immortal” is “No immortals are men” and that of the I proposition “Some man is mortal” is “Some mortal is man.”

In mathematics the term converse is used for the proposition obtained by the transformation of AB implies C into AC implies B, rendered symbolically as AB ⊃ C into AC ⊃ B. This operation may in some instances be reduced to the simple converse of an A proposition (universal affirmative) in the sense of traditional logic—for example: “Every equilateral triangle is equiangular,” and, conversely, “Every equiangular triangle is equilateral.” But such a reduction often becomes either impossible or very artificial. In this sense of conversion, the passage from a proposition to its converse is not, in general, a valid inference; and though often a mathematical proposition and its converse may both hold, separate proofs must be given for each case.