| Swords and knives, especially, were made to be directly proportional to the size of the user. |
| The ratio of the squares of the periods of two planets is directly proportional to the ratio of the cubes of the radii of their orbits. |
| Thus the intensity of fluorescence is directly proportional to the amount of nisin in the environment. |
| A culture's excitement about the web is directly proportional to that culture's alienation from its everyday experience. |
| The price of vineyard land is not directly proportional to the price fetched by grapes grown on it, however. |
| This offset depends on the angle of incidence, the index of refraction, and is directly proportional to the thickness of the slab. |
