The laws of physics usually relate one type of variable quantity to another. A physical law could tell us that as one variable (say, force) increases, another (say, acceleration) also increases proportionally by some factor. Physicists describe this type of relationship by saying that one variable quantity is proportional to another. Conversely, a physical law may stipulate that as one factor increases, another decreases by the same factor. Physicists describe this type of relationship by saying that the first variable quantity is inversely proportional to the other.
