Tentative (adjective)

1. Not certain or fixed; provisional.
2. Hesitant or uncertain in acting or speaking.

Origin:

From latin tentare "to try, to test".

Examples:

1. We have a tentative agreement.
2. The schedule is tentative and subject to change.
3. He made a tentative attempt to fix the problem.
4. She spoke in a tentative voice.
5. The plan is still in the tentative stages.