An inflection in someone's voice is a change in its tone or pitch as they are speaking.
例句
The man's voice was devoid of inflection...那人的聲音缺少抑揚變化。'Seb?' he said, with a rising inflection.“是塞伯嗎？”他揚聲問道。
N-VAR
(詞形的)屈折變化;屈折形式
In grammar, an inflection is a change in the form of a word that shows its grammatical function, for example a change that makes a noun plural or makes a verb into the past tense.