Ject对"painless" 的正确翻译：adj. 无痛的，不痛的。发音：['peinlis;peinlis]。例句参考：An instrument that in a painless and noninvasive manner uses the differential transmission and reflection of ultrasonic waves to create a detailed visual image of the brain. - 超声波心动描记器一种用来显示详细的大脑图象的仪器，利用超声波发送和反射的差异来测试并无伤无痛；