Example sentences
xiè谢xiè谢nǐ你！
Thank you!
xiè谢xiè谢nǐ你de的bāng帮zhù助。
Thanks for your help.
About this word
谢 on its own means to thank, and 谢谢 is that verb said twice. Reduplication is one of Chinese's favorite softening moves: it turns a bare action into something light and casual, the same trick behind 看看 (take a look), 说说 (talk it over), 试试 (give it a try). The doubled form also sounds more spoken than the single one. 谢谢 is the everyday thanks; 感谢 carries the same idea in a stiffer, more written register, the one you would meet in a formal letter. Answer it with 不客气 or 没关系.
The story behind the character
谢
谢 is 讠, the speech radical, plus 射 supplying the sound. Xu Shen wrote 謝，辤去也: to decline, to take your leave, and the thanking sense grew out of that. Both turning something down politely and thanking somebody happen with words. The simplified form kept the speech radical and folded 射 down into 身 and 寸.