5 sentences

1. 他的后背被雨淋湿了。

   tā de hòu​bèi bèi yǔ lín​shī le.

   His back was soaked by the rain.

   Source: Dong Chinese Dictionary

2. 我的后背有点痒痒，请帮我抓一下。

   wǒ de hòu​bèi yǒu​diǎn yǎng​yang, qǐng bāng wǒ zhuā yī​xià.

   My back is a bit itchy; please scratch it for me.

   Source: Dong Chinese Dictionary

3. 他轻轻抚摸着猫咪的后背，猫咪舒服地发出了叫声。

   tā qīng​qīng fǔ​mō zhe māo​mī de hòu​bèi, māo​mī shū​fu de fā​chū le jiào​shēng.

   He gently stroked the cat's back, and the cat purred contentedly.

   Source: Dong Chinese Dictionary

4. 我的后背被蚊子叮了一个包，抓挠了半天还是很痒。

   wǒ de hòu​bèi bèi wén​zi dīng le yī gè bāo, zhuā​nao le bàn​tiān hái​shi hěn yǎng.

   I have a mosquito bite on my back, and it's still very itchy even after scratching it for a long time.

   Source: Dong Chinese Dictionary

5. 他靠在椅子的后背上休息。

   tā kào zài yǐ​zi de hòu​bèi shàng xiū​xi.

   He rested by leaning against the back of the chair.

   Source: Dong Chinese Dictionary