melody和rhythm的区别主要在于含义及用法上。melody作为名词，含义为“旋律”、“曲调”、“歌曲”、“乐曲的音符编排”；乐曲的音符编排；rhythm作为名词，含义为“节奏”、“律动”、“规则变化;”、“节律”。

melody作为名词，译为旋律;曲调;(尤指)主旋律;(旋律简洁的)乐曲，歌曲;乐曲的音符编排。

例句：The melody is then taken up by the flutes.

接着由长笛奏主旋律。

Her voice was full of melody.

她的声音非常悦耳。

The melody that ran through his brain was composed of bad notes

回荡在他脑海里的旋律都走调了。

Peter played a delightful melody on his flute.

彼得用笛子吹奏了一支欢快的曲子。

The first violins introduced the first theme, a soft and beautiful melody.

第一小提琴奏出第一主题，旋律轻柔动听。

He played an Irish melody on the harp.

他用竖琴演奏了一首爱尔兰曲调。

Lyrics are important. They're just not as important as melody.

歌词是重要的，只是没有旋律那么重要。

rhythm作为名词，译为节奏;韵律;律动;规则变化;规律;节律。

例句：He can't seem to play in rhythm .

他的演奏好像不合节拍。

Begin to listen to your own body rhythms.

开始聆听你自己身体的节奏。

The trace showed a normal heart rhythm.

描记图表明心率正常。

A basic sense of rhythm and pitch is essential in a music teacher.

基本的韵律感和音高感是音乐教师的必备素质。

The boat rocked up and down in rhythm with the sea.

小船随着海浪起伏有致。

The ship adjusted herself to the roll and rhythm of the sea.

船随着海水的起伏节奏时起时落。

They've revivified rhythm and blues singing by giving it dance beats.

他们为节奏布鲁斯的歌曲中加入了舞曲的节奏，使之变得更加活跃。