1.
A person’s ~ of something is the amount of it that they use. (TECHNICAL)
The drug increases the number of red cells in the blood, enhancing oxygen ~ by 10 percent.
...research in relation to the ~ of nitrate into vegetables.
N-SING: usu with supp
2.
You say that someone is quick on the ~ when they understand things quickly. You say that someone is slow on the ~ when they have difficulty understanding simple or obvious things.
She is not an intellectual, but is quick on the ~...
Carol was absent-minded and a little slow on the ~.
PHRASE: v-link PHR