However, if you are looking for a related prefix, you could consider:
* Deci-: This prefix means "tenth" and is often used in scientific contexts, like "decimeter" (one-tenth of a meter). While not directly related to "decisive," it comes from the same Latin root.
* Decad-: This prefix means "ten" and is used to describe a period of ten years. Again, not directly related to "decisive," but it shares a common root.
If you are trying to create a word with a similar meaning to "decisive," you would need to construct a new word or phrase using different prefixes and roots. For example, you could use "firm," "resolute," "definitive," or "conclusive."