不 (bú): The character for “not” or “no.” Normally pronounced as `bù` (fourth tone), it changes to `bú` (second tone) when it comes before another fourth-tone character, like `用 (yòng)`.
用 (yòng): This character means “to use” or “to need.”
谢 (xiè): This character means “to thank.” It's the same character found in “谢谢” (xièxie).
When combined, 不用谢 (bú yòng xiè) creates the literal meaning “no need to thank.” This reflects a common politeness strategy in Chinese culture: deflecting praise or thanks to show humility.