Simple:
* My phone contract is up for renewal, so I'm going to request an extension.
* The library offered me an extension on my overdue book.
* We need an extension on the deadline for this project.
More complex:
* The construction project required a significant extension of the original timeline.
* The house features a beautiful sunroom, which serves as a cozy extension of the living space.
* The company's recent extension into the international market has been successful.
Figurative:
* The artist's use of color was a brilliant extension of his unique style.
* The new software offers an extension of the previous version's capabilities.
Choose the sentence that best fits your intended meaning and context.