In Chinese tradition certain numbers are believed by some to be auspicious (吉利, pinyin: jílì; Cantonese Yale: gātleih) or inauspicious (不利, pinyin: bùlì; Cantonese Yale: bātleih) based on the Chinese word that the number sounds similar to. The numbers 6, 8, and 9 are generally considered to be auspicious, while 4 and 7 are considered inauspicious.

The number 7 (七, pinyin: qī) in Mandarin sounds like "even" in Mandarin (齊, pinyin: qí), so it is a good number for relationships. It also sounds like "arise" (起, pinyin: qǐ) and "life essence" (氣, pinyin: qì) in Mandarin. Seven can also be considered an unlucky number since the 7th month (July) is a "ghost month". It also sounds like "to deceive" (欺, pinyin: qī) in Mandarin. 

No. 7 in Chinese Culture
 

In the traditional Chinese culture, seven represents the combination of Yin, Yang and Five Elements (Metal, Wood, Water, Fire and Earth). This combination is considered as “harmony” in the ideology of Confucianism. While in Chinese Taoism, it stands for Tao which has a close connection with kindness and beauty.

 

Seven was widely used in ancient Chinese culture, for example the Seven Treasures for Buddhist Scripture refer to gold, silver, colored glaze, coral, amber, seashell, and agate. Another example is the Double Seventh Festival when the Milky Way Lovers (the Cowherd and the Weaving Maid) can have their annual meeting only on July 7th. As a Chinese legend goes, when the Jade Emperor in Heaven learnt that his beloved daughter, Weaving Maid, had married a poor cowherd and lived a happy life, he created the Milky Way to separate the lovers. After that, only on the seventh day of the seven month each year, the Cowherd and the Weaving Maid got a chance to meet on the Magpies Bridge which was formed over the Milky Way by a large number of magpies. Therefore, July 7th is regarded as the Chinese Valentine’s Day.
 

Although seven is generally considered a propitious number, it is at times disliked in China. The July 7th Incident of 1937 (also named Marco Polo Bridge Incident) always reminds Chinese people of the painful history of the eight-year’s Sino-Japanese War. 7 has the same pronunciation with 欺, Qi in Chinese, meaning cheating, lying to, or riding roughshod over someone. When choosing a telephone number or something like that, 7 is often left out of the list. The Seven Year Itch, the famous American movie, has long been a popular saying in China to describe the unsteady period of a marriage. It means that in the seventh year of a marriage, the couple faces serious problems in their relationship. Once a bit of negligence or unwise action is taken, their marriage may end up in the same year.