Endings

Hello, I know that there are different endings depending upon the required level of politesness. However, there seem to be other endings to Korean sentences that I am not understanding when to use. Such ni at the end, and likewise, is there a resource you can send me, or a quick explanation (outside of the simnida, seyo, etc endings). Thank you very very much.

안녕하세요 Amie! You might find this website helpful: http://www.teachenglishinasia.net/korean-verb-ending-database Please let me know if you have any questions! - Sujung