Bionics is the science of combining natural biological systems with technology. When an engineer designs a boat with an outer "skin" that mimics a dolphin's skin, she uses bionics.
Today's science, medicine, and engineering fields all use bionics in various ways. Many prosthetic limbs are designed through bionics — in other words, they are engineered using biological structures like limbs, joints, and nerves, as well as modern technology. A person who's lost an arm and had it replaced with a bionic one can even learn to control it using her mind. Most experts describe bionics as a portmanteau of biology and electronics.