Used to introduce additional information or change the subject to something related but not central to the main conversation.
This phrase originated in the 14th century from the literal sense of 'by the way' meaning along the path or route. It evolved metaphorically to mean something mentioned in passing during the course of a conversation, like a traveler noting something seen along their journey.
The phrase is a masterful conversation tool that allows speakers to introduce new topics without seeming abrupt or disconnected. Interestingly, what follows 'by the way' is often not actually 'by the way' at all - it's frequently the real point the speaker wanted to make, making it a polite form of conversational strategy.
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