Etymology: The word “interjection” comes from Latin word “interiectio” means “a throwing of placing between”. But, it denotes somewhat different meaning in grammatical view.
Definition: The words which express sudden feelings of mind such as, abhorrence, unpleasantness, soreness, merriment, anger etc. called interjection.
An interjection is a word or sound thrown into a sentence to express some feeling of the mind. J.C – Nesfield.