There are various entries for both but for one, Merriam-Webster says that resentment is "a feeling of anger or displeasure about someone or something unfair." For the second word, it says "a strong feeling of anger toward someone that lasts for a long time."
My question is, does "unfairness" play a role in holding a grudge also? And secondly, is the main difference between the two the matter of time or also intensity?
For instance, let's say a neighbor makes noises at night, I might be angry and if I feel it's unfair that they do that and I can't or that the building manager doesn't care, I assume that's resentment. But what makes it a grudge? Is it related to it happening often? To my resentment being real intense and not being able to forgive them?
Thanks.