Simple:
* There was a variation in the color of the leaves on the tree.
* The recipe called for a variation in the amount of sugar used.
* The singer's performance showed a surprising variation in style.
More complex:
* The study revealed a significant variation in the response rates between the two groups.
* The architect designed a variation on the traditional house plan, adding a modern twist.
* The artist's work explored the variation of light and shadow in different settings.
* Due to natural variations, the time of sunset can change slightly each day.
Figurative:
* Her singing voice was a variation on the traditional folk music she grew up with.
* The new policy represented a variation on the old, but with some important changes.
* His latest novel was a variation on a theme he had explored in his earlier work.
The meaning of "variation" will depend on the context of the sentence, but generally it refers to a difference or change compared to something else.