The suffix -san is an honorific suffix used after a personal name, having the meaning that Mr., Mrs., Miss, and Ms. do in English.
The suffix "san" is typically added to people's names who are of equal social status, the suffix "sama" is added to the names of people of higher social status. The suffix "kun" is added to the names of young boys and "chan" is typically added to the names of young girls and babies.
See also http://www.asahi-net.or.jp/~IF2N-SZK/j1.html, http://www.japancorner.com/etiquette-manners.asp and http://kuroi-hoshi.org/jap.html.
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