"Changeableness" refers to the state or quality of being constantly changing or unpredictable. Synonyms for this word include instability, variability, fluctuation, unpredictability, mutability, oscillation, inconstancy, and unreliability. These words all suggest a lack of consistency or predictability in something, whether that be a person's behavior or the weather. "Fluctuation" refers specifically to significant changes or variations in something, while "mutability" suggests a tendency to change and alter over time. "Inconstancy" and "unreliability" both imply a lack of dependability or consistency in something, making them particularly fitting for describing fickle people or volatile situations.