Two distinct types of Chinese surnames existed in ancient China, namely xing () or ancestral clan names, and shi () or branch lineage names. Later, the two terms began to be used interchangeably, and now, "xing" refers to the surname while "shi" may be used to refer to the clan name or maiden name. The two terms may also be used together as "xingshi" for family names or surnames. Most Chinese surnames ("xing") currently used were originally "shi". The ancient "xing" surname is believed to be matrilinear, but Han Chinese family name has been exclusively patrilineal for over two thousand years, passing from father to children. This system of patrilineal surnames is unusual in the world in its long period of continuity and depth of written history, and Chinese people may view their surnames as part of their shared kinship and Han Chinese identity. Women do not normally change their surnames upon marriage, except sometimes in places with more western influences such as Hong Kong. Traditionally Chinese surnames have been exogamous in that people tend to marry those with different last names.