Number + 章
章 (zhāng) is a classifier used to count chapters or sections of a book, document, or figurative stage in life. It is placed after a number, as in 第一章 (Chapter 1). It can also be used metaphorically to describe a new phase or period, as in 新的一章 (a new chapter).
这本书一共有十二章。
zhè běn shū yígòng yǒu shí'èr zhāng.
This book has twelve chapters in total.
请大家翻到第三章,我们开始上课。
qǐng dàjiā fān dào dì sān zhāng, wǒmen kāishǐ shàngkè.
Everyone please turn to chapter three; let's begin class.
毕业后,他的人生翻开了新的一章。
bìyè hòu, tā de rénshēng fānkāi le xīn de yì zhāng.
After graduating, his life opened a new chapter.