significant figures
noun [ plural ] mathematics UK specialized uk/sɪɡˌnɪf.ɪ.kənt ˈfɪɡ.əz/ us/sɪɡˌnɪf.ɪ.kənt ˈfɪɡ.jɚz/ (US significant digits)
有效数字
the numbers used to write a number to be as exact as is needed
2.3945 to two significant figures is 2.4. 2.3945保留两位有效数字就是2.4。