Unalterable (adjective)

Not capable of being changed or modified.

Origin:

From un- + alterable.

Examples:

1. The laws of physics are unalterable.
2. His unalterable resolve was evident in the way he held himself.
3. The unalterable decision of the court was final.
4. The unalterable facts of the case were clear.
5. His unalterable opinion on the matter was well known.