She becomes quiet. ☊ 
Cô ấy trở nên yên lặng. ☊ Adjectives 2 like: yên lặng → →
He didn't move a muscle (= stood completely still). ☊ muscle ☊
She crept downstairs (as) quiet as a mouse. ☊ quiet ☊
yên lặng làm dịu đi sự yên lặng sự êm ả 
calm lặng yên lặng yên tĩnh quiet lặng yên lặng yên tĩnh quietly She becomes quiet. ☊ Cô ấy trở nên yên lặng. ☊ Adjectives 2