Suppose you have two friends who don’t know each other. You introduce them and leave them alone. Nothing happens. They can’t seem to get together. Then you join the company and, when all three of you are together, your two friends suddenly take to each other. In this situation you have been a “catalyst!” In science or chmistry, a catalyst is a substance Which by its mere presence hastens or slows a chemical change. Suppose a manufacturer wants to produce a certain chemical compound synthetically, that is, by combining simpler substances to form it. He often finds that these simpler substances will not combine at all, or will combine too slowly to be of use. So he adds a catalyst.