What is Thank ?
Thank is (verb) 1. to say or do something that shows you are grateful to someone for doing something for you She thanked the policeman for helping her to cross the street. Don’t forget to thank Aunt Ann for her present. 2. thank goodness! or God! or heavens! expressions used to show relief Thank goodness it didn’t rain for the school sports day! Thank God the ambulance turned up quickly!
source: Easier English, Student Dictionary Upper Intermediate Level