An interjection is a word added to a sentence to convey an emotion or a sentiment such as surprise, disgust, joy, excitement, or enthusiasm. It is not grammatically related to any other part of the sentence.
Read more at http://www.grammar-monster.com/lessons/interjections.htm#31CxVe413WxZkffH.99
Read more at http://www.grammar-monster.com/lessons/interjections.htm#31CxVe413WxZkffH.99