An Etymological Dictionary of Astronomy and Astrophysics

1. Math.: A mathematical quantity obtained from a given quantity by an algebraic, geometric, or functional transformation.
   The transformation itself.
   

2. To change in form, appearance, or structure; to change in condition, nature, or character; convert.
   Physics: To change into another form of energy.
   

To increase or decrease (the voltage and current characteristics of an alternating-current circuit), as by means of a transformer.
Math.: To change the form of (a figure, expression, etc.) without in general changing the value.

See also: → trans- + → form.