General justifications:
* Justification: This is the most common and direct translation of the verb.
* Rationale: This emphasizes the reason or logic behind something.
* Reason: This is a simple and straightforward word for the cause or explanation.
* Defense: This implies a justification in the face of criticism or accusation.
* Explanation: This emphasizes the act of making something clear.
Specific justifications:
* Exculpation: This specifically refers to justifying oneself from blame or guilt.
* Vindication: This refers to proving someone's innocence or the correctness of their actions.
* Legitimization: This refers to making something lawful, proper, or acceptable.
The best noun to use will depend on the specific context and the nuance you want to convey.