Chiasmus
A crossed construction (AB-BA) where two expressions mirror each other in reversed order.
Chiasmus arranges two groups of words in mirror image, on an AB-BA pattern: "eat to live, not live to eat." The crossing creates a sonic and logical symmetry that lends the sentence an air of definitive truth — it is the figure of maxims and memorable formulas.
Beyond the sentence, chiasmus can structure a scene or an entire narrative: two characters who swap positions (master becomes slave, student surpasses teacher) trace a narrative chiasmus. The figure then carries deep meaning: reversal, the reversibility of fates.
Example
"Ask not what your country can do for you — ask what you can do for your country."