General:
* Nuance: A subtle difference in meaning or expression.
* Subtlety: A delicate or fine distinction, often difficult to perceive.
* Gradation: A gradual change or difference in degree or intensity.
* Refinement: A slight improvement or enhancement that makes something more precise or refined.
* Distinction: A difference or contrast, especially a subtle one.
More Specific:
* Shading: A subtle variation in meaning, especially one that is created by the context.
* Undercurrent: A hidden or implicit meaning that runs beneath the surface of the text.
* Implication: A suggestion or hint that is not explicitly stated.
* Overtone: A subtle suggestion or association that is conveyed by a word or phrase.
More Formal:
* Semantic variation: A difference in the meaning of words or phrases.
* Lexical distinction: A difference in the meaning of words.
Informal:
* Nitpicky: Focusing on minor details or differences.
* Splitting hairs: Making a distinction that is too fine or subtle.
The best word to use will depend on the specific context and the type of difference you are trying to describe.