A Chinese style name, sometimes also known as a courtesy name (Chinese: 字; pinyin: Zì), is a given name to be used later in life. After 20 years of age, the zì is assigned in place of one's given name as a symbol of adulthood and respect. Primarily used for male names, one could be given a zì by the parents, or by their first personal teacher on the first day of family school, or one may adopt a self-chosen zì. The tradition of using style names has been fading since the May Fourth Movement in 1919. There are two common forms of style name, the zì and the hào.
Zì (adult name) 
The zì, sometimes called the biǎozì or "courtesy name", is a name traditionally given to Chinese males at the age of 20, marking their coming of age. It was sometimes given to females upon marriage. As noted above, the practice is no longer common in modern Chinese society. According to the Book of Rites (traditional Chinese: 禮記; simplified Chinese: 礼记), after a man reaches adulthood, it is disrespectful for others of the same generation to address him by his given name, or míng. Thus, the given name was reserved for oneself and one's elders, while the zì would be used by adults of the same generation to refer to one another on formal occasions or in writing; hence the term "courtesy name".
The zì is mostly disyllabic (comprises two characters) and is usually based on the meaning of the míng or given name. Yan Zhitui (顏之推) of the Northern Qi Dynasty believed that while the purpose of the míng was to distinguish one person from another, the zì should express the bearer's moral integrity.
The relation which often exists between a person's zì and his míng can be seen in the case of Mao Zedong (traditional Chinese: 毛澤東; simplified Chinese: 毛泽东), whose zì was Rùnzhī (traditional Chinese: 潤之; simplified Chinese: 润之). These two characters share the same radical - 氵, which signifies water. Both characters can mean "to benefit" or "to nourish".
Another way to form a zì is to use the homophonic character zǐ (Chinese: 子; pinyin: zǐ) - a respectful title for a male - as the first character of the disyllabic zì. Thus, for example, Gongsun Qiao's zì was: Zǐchǎn (traditional Chinese: 子產; simplified Chinese: 子产), and Du Fu's: Zǐméi (子美).
It is also common to construct a zì by using as the first character one which expresses the bearer's birth order among male siblings in his family. Thus Confucius, whose actual name was Kǒng Qiū (孔丘), was given the zì Zhòngní (仲尼), where the first character zhòng indicates that he was the second son in his family. The characters commonly used are bó (伯) for the first, zhòng (仲) for the second, shū (叔) for the third, and jì (季) typically for the youngest, if the family consists of more than three sons.
The use of zì began during the Shang Dynasty and slowly developed into a system, which became most widespread during the succeeding Zhou Dynasty . During this period, women were also given zì. The zì given to a woman was generally composed of a character indicating her birth order among females siblings and her surname. For example, Mèng Jiāng (孟姜) was the eldest daughter in the Jiāng family.
Prior to the 20th century, sinicized Koreans, Vietnamese, and Japanese were also referred to by their zì.
The zì of some famous people:
||Bó Yáng (伯陽)
|Cao Cao 曹操
|Liu Bei 劉備
|Sima Yi 司馬懿
|Zhuge Liang 諸葛亮
|Li Bai 李白
|Tang Yin 唐寅
|Sun Yat-sen 孫逸仙
||Zai zhi (載之)
|Mao Zedong 毛澤東
|Yue Fei 岳飛
Hào (pseudonym) 
Hào (simplified Chinese: 号; traditional Chinese: 號; pinyin: hào; Japanese gō; Korean: ho; Vietnamese: hiệu) is an alternative courtesy name, usually referred to as the pseudonym. It was most commonly three or four characters long, and may have originally become popular due to people having the same zì. A hào was usually self-selected and it was possible to have more than one. It had no connection with the bearer's míng or zì; rather it was often a very personal, sometimes whimsical, choice perhaps embodying an allusion or containing a rare character, as might befit an educated literatus. Another possibility was to use the name of one's residence as one's hào; thus Su Shi's hào Dongpo Jushi (i.e., "Resident of Dongpo" ("Eastern slope"), a residence he built while an exile in Sichuan). An author's hào was also often used in the title of his collected works (also called Bi Ming literally pen name).
See also