What is a Character Arc?
The definition of a character arc is thought to be something to do with how the main protagonist or hero/heroine changes within a story. In some respect this is correct, it is inaccurate to assume that this means every main character needs to undergo some major alteration. Recognising the difference between growth and change is crucial to the proper implementation of the character arc in a novel.
Main characters do indeed need to grow. A story cannot grow naturally if the primary characters within it do not develop and adjust to the shifting moving tides. When a story advances from one area of exploration to the next, the main character needs to update also. That method is how stories work. Therefore, it is easy to see how the growth, and the main character’s progress, is inherent in the mechanisms that progress a novel.
When you discuss change and how the main character “has” to change, you’re making an assumption about the characteristics of that growth. Not all growth is transformative. Sometimes a character can grow by supporting their status, shoring up their resolve against whatever is hurled at them. This is no less significant than the sort of growth where someone develops who they are or how they see the world.
Crime Fiction: Hardboiled Detective 