Something that is ~ changes quite often, and there usually seems to be no fixed pattern to these changes.
The potassium content of foodstuffs is very ~...
...a ~ rate of interest.
There’s a great deal of variability between individuals.
A ~ is a factor that can change in quality, quantity, or size, which you have to take into account in a situation.
Decisions could be made on the basis of price, delivery dates, after-sales service or any other ~...
A ~ is a quantity that can have any one of a set of values. (TECHNICAL)
It is conventional to place the independent ~ on the right-hand side of an equation.