それなら + [sentence]
Note: Standalone discourse connector used at the beginning of a sentence, responding to a previous statement. それ refers back to what was just said.
それなら means "if that's the case" or "if so" and is used to respond to something the listener has just heard or learned. The speaker takes the previous statement as a given condition and then offers a suggestion, conclusion, or follow-up based on it. It functions as a conversational connector that builds on shared context.
それなら typically appears at the beginning of a sentence, responding to information that was just provided.
While もし〜~なら introduces a hypothetical condition that may or may not be true, それなら responds to something that has already been stated or is accepted as fact. The speaker is not speculating – they are building on what they just heard.
それなら is relatively neutral in formality and works in both casual and polite contexts. More casual alternatives include それじゃ and だったら. A more formal equivalent is それでしたら or そうであれば.
In casual speech, それなら is often shortened to just なら when the context is clear.