Phono-semantic — one part hints at the meaning, another at the sound
Example phrases
这件礼服的纽扣全部由贝壳打磨而成,细节十分考究。Zhè jiàn lǐfú de niǔkòu quánbù yóu bèiké dǎmó ér chéng, xìjié shífēn kǎojiu.The buttons on this formal dress are all polished from shells, and the details are very refined.
外套上掉了一颗纽扣,我得缝上去。Wàitào shàng diào le yì kē niǔkòu, wǒ děi féng shàngqù.A button has come off my coat, and I have to sew it back on.
小宝宝还不会自己扣纽扣。Xiǎo bǎobao hái bú huì zìjǐ kòu niǔkòu.The little baby cannot do up buttons by himself yet.