General:
* Optional: Means something is not required, indicating a choice.
* Alternative: Suggests there are other choices available.
* Voluntary: Implies a choice is made freely.
* Available: Emphasizes that the option is present and ready to be chosen.
More specific:
* Discretional: Implies the option is subject to individual judgment or preference.
* Elective: Relates to choices made by the individual.
* Selectable: Highlights the ability to choose.
* Negotiable: Indicates the option is open to discussion and change.
More figurative:
* Open-ended: Suggests flexibility and possibility.
* Flexible: Indicates a wide range of choices.
* Multifaceted: Describes an option with various aspects or possibilities.
The best adjective to use will depend on the context of your sentence and the specific nuance you want to convey.