肩膀 (jiānbǎng) is the standard Chinese word for "shoulder." It frequently appears in phrases describing physical contact or gestures, such as 拍他的肩膀 (pat his shoulder) or 肩膀很宽 (broad shoulders).
他的肩膀很宽,穿什么衣服都好看。
Tā de jiānbǎng hěn kuān, chuān shénme yīfu dōu hǎokàn.
His shoulders are broad — he looks good in anything.
我背了一天的包,肩膀特别酸。
Wǒ bēi le yī tiān de bāo, jiānbǎng tèbié suān.
I carried a bag all day, and my shoulders are really sore.
她把头靠在他的肩膀上休息了一会儿。
Tā bǎ tóu kào zài tā de jiānbǎng shàng xiūxi le yīhuìr.
She rested her head on his shoulder for a while.