Segment Lengths
1. The problem is to express the relationship between the lengths of segments $AB$, $BC$, and $AC$ such that $|AB| = |BC| \neq |AC|$.
2. The absolute value notation $|XY|$ represents the length of the segment connecting points $X$ and $Y$.
3. Writing $|AB| = |BC|$ means the length of segment $AB$ is equal to the length of segment $BC$.
4. The notation $|AB| \neq |AC|$ means the length of segment $AB$ is not equal to the length of segment $AC$.
5. Combining these, $|AB| = |BC| \neq |AC|$ reads as "the length of $AB$ equals the length of $BC$, but both differ from the length of $AC$."
6. This is already the standard and correct mathematical notation to describe such a relationship between the segment lengths.
7. Therefore, you write the relationship exactly as $|AB| = |BC| \neq |AC|$.