说到 谈到
Pattern
说到 / 谈到 + topic，comment
Key words
Core idea
说到 and 谈到 introduce a topic.
They mean “speaking of,” “when it comes to,” or “talking about.”
Usage feel
说到 is common and conversational.
谈到 can feel a little more topic-focused or discussion-like.
Usage boundary
These are discourse markers. They set up a topic for the next comment rather than simply reporting that someone spoke.
Examples
说到台湾，我想到夜市。
Shuōdào Táiwān, wǒ xiǎngdào yèshì.
Speaking of Taiwan, I think of night markets.
谈到工作，他很认真。
Tándào gōngzuò, tā hěn rènzhēn.
When it comes to work, he is very serious.
说到考试，我有点紧张。
Shuōdào kǎoshì, wǒ yǒu diǎn jǐnzhāng.
Speaking of the exam, I am a little nervous.
Common mistakes
Avoid
说台湾到，我想到夜市。
Use
说到台湾，我想到夜市。
到 follows 说 or 谈 in this discourse marker.
Seen in stories
The Comment Section Plan
说到危机沟通，经理认为透明比解释更重要。
Speaking of crisis communication, the manager believed transparency mattered more than explanation.
The Rooftop Key
说到顶楼，住户们有的晒棉被，有的种九层塔，谁都说自己没拿钥匙。
Speaking of the rooftop, some residents dry quilts there and some grow basil, but everyone said they had not taken the key.
The Rooftop Bento Party
说到那位外送员，大家决定另外留一个便当给他。
Speaking of that delivery rider, everyone decided to save an extra bento for him.
The Wrong Locker Code
说到网购，邻居们什么都买，可是谁也不承认这袋猫粮是自己的。
Speaking of online shopping, the neighbors buy everything, yet no one admitted the cat food was theirs.