‘当初’ is an adverb meaning 'originally', 'at first', or 'back then'. It refers to the beginning of a past event, situation, or period — often with a sense of contrast to how things turned out later. The character 当 (dāng) here functions as a temporal marker meaning 'at (a certain time)', while 初 (chū) means 'beginning' or 'initial stage'; together, they literally convey 'at the beginning'. It’s commonly used in reflective or narrative contexts, especially when recounting decisions, intentions, or conditions that preceded later developments.

This word frequently appears at the start of a clause or sentence and is often followed by a verb phrase describing what was true or intended initially. It carries a subtle tone of retrospection — sometimes implying regret, surprise, or irony about how reality diverged from early expectations. While not formal per se, it’s more common in written Chinese and spoken narratives than in casual daily conversation.