There are lots of words we could use.
Revisions. Amendments. Tweaks. Updates.
All nouns, the thing itself, but you’re doing something when make your corrections. Often it’s framed as a final hurdle, grumble grumble, a bit more work from the examiners and the PhD process. I think the best word to focus on is “improvements” – your examiners have spotted some ways that you can make your thesis better.
Of course, ten years ago, when I started my corrections I did not think of them as improvements. I gritted my teeth and got to work, but felt frustrated. “Why do I have to do this now? Weren’t the last three and a half years enough?”
No. They weren’t. A few more weeks was all it took and my thesis was better as a result, and that’s the point of corrections. Your examiners want to help you make your thesis the best presentation of your research that it can be.
You might not feel that way when you get your list of corrections (or revisions, improvements and so on) but I hope you will by the end.
Ten years later I feel grateful my examiners gave me the opportunity to help my thesis be better.