Phono-semantic — one part hints at the meaning, another at the sound
Example phrases
周末的公园里人山人海,连走路都很困难。Zhōumò de gōngyuán li rénshān rénhǎi, lián zǒulù dōu hěn kùnnan.The park is packed with people on weekends, and it is hard even to walk.
春节前的火车站总是人山人海。Chūnjié qián de huǒchēzhàn zǒngshì rénshān rénhǎi.The railway station before the Spring Festival is always a sea of people.
演唱会现场人山人海,大家都在跟着唱歌。Yǎnchànghuì xiànchǎng rénshān rénhǎi, dàjiā dōu zài gēn zhe chànggē.The concert venue was packed with people, and everyone was singing along.