Conversion, n.
Etymology: [L. conversio: cf. F. conversion. See Convert.]
1. The act of turning or changing from one state or condition to another, or the state of being changed; transmutation; change. Artificial conversion of water into ice. Bacon. The conversion of the aliment into fat. Arbuthnot.
2. The act of changing one's views or course, as in passing from one side, party, or from of religion to another; also, the state of being so changed. "Conversion to Christianity." Prescott.
3. (Law)
An appropriation of, and dealing with the property of another as if it were one's own, without right; as, the conversion of a horse. Or bring my action of conversion And trover for my goods. Hudibras.
7 more senses
4. (Logic)
The act of interchanging the terms of a proposition, as by putting the subject in the place of the predicate, or the contrary.
5. (Math.)
A change or reduction of the form or value of a proposition; as, the conversion of equations; the conversion of proportions.
6. (Mil.) (a) A change of front, as a body of troops attacked in the flank. (b) A change of character or use, as of smoothbore guns into rifles.
7. (Theol.)
A spiritual and moral change attending a change of belief with conviction; a change of heart; a change from the service of the world to the service of God; a change of the ruling disposition of the soul, involving a transformation of the outward life. He oft Frequented their assemblies, . . . and to them preached Conversion and repentance, as to souls In prison under judgments imminent. Milton.
Shades of meaning
Fernald has no entry of its own for conversion; he lists it under change.
Where he writes about it:
For the distinctions between the other words compare the synonyms for change, v. In the religious sense regeneration is the vital renewing of the soul by the power of the divine Spirit; conversion is the conscious and manifest change from evil to good, or from a lower to a higher spiritual state; as, in Luke xxii, 32, "when thou art converted, strengthen thy brethren." In popular use conversion is the most common word to express the idea of regeneration. — from change