A must learn word. You should always be polite and say thank you!
Thank you شُكْراً shuk-ran
|Part of speech||Root |
If you want to be extra emphatic you can say the following:
Thank you شُكْراً shuk-ran abundantly جَزِيلاً Ja-zee-lan
Here are some other examples of words you can use to be polite: Wikibooks - Being Polite. I may be able to cover more of them in future posts.
 - Wikitionary about root of Thank You