adj.向下流的
n.向下流的部分

Defluent is not an English word. It appears to be a combination of the prefix "de-" (which often indicates reversal or removal) and the noun "fluent," which refers to someone who can speak a language easily and effectively, or to a flowing substance. However, "defluent" does not have a recognized meaning in English. Here are ten sentences using correct English words:
She speaks English fluently.
她英语说得流利。
The river's deflection from its original course changed the landscape significantly.
河流偏离原来的河道显著改变了地貌。
He was fluent in three languages: English, Spanish, and French.
他会说三种语言：英语、西班牙语和法语。
The deflection of the ball by the goalkeeper prevented a certain goal.
守门员挡球的动作阻止了对方必进的一球。
Her fluency in Mandarin helped her land the job in Beijing.
她在普通话方面的流利帮助她在在北京找到了工作。
The deflection of light by a massive object is a prediction of Einstein's theory of general relativity.
光线被大质量物体偏折是爱因斯坦广义相对论的一个预言。
He has become fluent in Japanese after living in Tokyo for several years.
他在东京住了几年后，日语变得流利了。
The deflection of charged particles in a magnetic field is used in mass spectrometry.
带电粒子在磁场中的偏转在质谱分析中得到应用。
Her fluency in German opened up many opportunities for her in Europe.
她在德语方面的流利为她在欧洲打开了许多机会。
The deflection of ocean currents can have significant impacts on global climate.
海洋洋流的偏移会对全球气候产生重大影响。