Conversion means changing something from one form, purpose, or belief into another. When you convert miles to kilometers in math class, you're expressing the same distance in a different measurement system. When someone converts their attic into a bedroom, they're transforming unused storage space into a place where people can sleep.

The word appears in many contexts. In sports, a conversion happens when a team successfully completes an extra point after a touchdown or scores after getting close to the goal line. In religion, conversion means adopting a new faith or belief system, often after serious thought and study. A factory might undergo conversion when it switches from making one product to making something completely different, like when car manufacturers converted to making tanks and airplanes during World War II.

The process of conversion usually requires effort and can involve several steps. Converting a recipe that serves four people into one that serves twelve means carefully multiplying each ingredient. Converting Fahrenheit to Celsius requires a specific formula.

The related word convertible describes something that can be changed from one form to another, like a convertible sofa that transforms into a bed, or a convertible car whose roof can fold down. Someone who converts to a new religion or way of thinking is called a convert.