そういえばSpeaking of which, By the way, Come to think of it

そういえば is a hypothetical structure in Japanese consisting of the adverb そう 'like that', and the ば conjunctive form of the う-Verb 言(い)う 'to say'. Common translations include 'speaking of which', 'by the way', and 'come to think of it'. These translations are actually very close to the literal translation of 'if saying that' in that they all refer back to the previous statement as being a trigger for bringing up a topic that the speaker wants to discuss.

そういえば will primarily appear at the beginning of sentences, before the speaker will then bring up the topic that they were reminded of.

Caution

Due to そういえば refering to something that has already been brought up over the course of a conversation, it will not be used to move on to completely unrelated topics in the same way that phrases like 'by the way' are used in English.

Fun-fact

そういえば is very similar in the way it is used to といえば, with そう simply replacing the direct quotation of と. Many textbooks will list both as a single grammar point, despite そういえば itself basically being a set phrase.