The Japanese adverb 'いつのまにか (itsunomanika)' means 'unnoticed' or 'before one realizes'. It is used to describe something that happens gradually or without being noticed. This word often conveys a sense of surprise or realization about how something has changed over time. For example: The seasons changed unnoticed「いつのまにか季節が変わっていた」(いつのまにかきせつがかわっていた). Before I knew it, he had grown up「いつのまにか彼は大人になっていた」(いつのまにかかれはおとなになっていた). This adverb is commonly used in both casual and formal contexts to express subtle changes or developments.