A reduced thing has been lessened or subtracted from. If you want to ride your bike in Italy and you’re on a budget, look for reduced airfare. For a reduced risk of injury, wear a helmet when you get there.
To reduce something is to make it smaller or lessen it in some way. Therefore, anything reduced is smaller than it was before. If you’re pedaling your way through Italy and hit a giant hill, you’ll probably have reduced pedal power and go much slower. This word applies to things that are going down in degree or amount. There could be reduced pain, reduced cost, or reduced size. Anything described as reduced can also be called decreased.