0, N-, si--redup/mag--redup
To trade; to exchange; to change a law.
The root unaffixed is reciprocal and means to trade s.t. for s.t. else. With the si--RED it is also reciprocal but refers more to business dealings in exchanging goods.
He exchanged his slippers because when he bought them they already had a defect in them.
The reason the Philippines and Sabah have improved is because they are fond of trading goods with each other.
If you are willing, I will trade my cow for your motorcycle.