そういえば

そういえば is used when you recall or bring up something related to the current topic, often to transition to a related memory or to introduce a new but relevant remark. It softens the shift in topic and signals that you are remembering something relevant to the ongoing conversation. It is casual and common in spoken Japanese or informal writing; in more formal contexts, you might simply say ところで or そう言えば. Typical usage is at the start of a sentence following a pause or a shift in topic, not as a main point of discussion itself.