とは

とは is used to define, explain, or emphasize what precedes it, often with a sense of surprise, disbelief, or emphasis. It marks the preceding item as something being defined, clarified, or contrasted with the listener’s expectations. It can express that the speaker is reacting to information as a notable or surprising fact, or it can introduce a general statement about what something is. In many cases, the rest of the sentence conveys the speaker’s reaction or assessment (e.g., 信じられない, 予想外だ). It frequently appears in written Japanese or formal spoken contexts, and can be used after nouns, phrases, or even entire clauses.