Any subsitutes for the phase "free will"?

Question

I am doing a reaearch paper on it and i need so words or phrases to replace free will

Answer 1

Voluntary, voluntarily (depending on how you are using it in the sentence).

If you mean it as a noun (like saying that people have free will), it's a pretty technical term. Nothing else will have the exact same meaning, so you'll have to just keep using it.