Which word describes someone who changes moods unpredictably?

The term "capricious" is used to describe someone whose mood or behavior can change suddenly and unpredictably, often without logical reasoning. This word originates from the idea of a caprice, which means a whimsical or fanciful notion. Individuals described as capricious may exhibit erratic emotional swings, making their responses and actions difficult to anticipate.

In contrast, the other terms like "stable," "consistent," and "reliable" all imply a sense of steadiness and predictability. A stable person maintains a consistent emotional state, while someone who is consistent or reliable demonstrates dependability in their behavior and reactions. Therefore, these words serve as opposites to what "capricious" communicates. Understanding these distinctions clarifies that "capricious" aptly captures the essence of unpredictable mood changes.