An exclamation (also called an interjection) is a word or phrase that expresses strong emotion, such as surprise, pleasure, or anger. Exclamations often stand on their own, and in writing they are usually followed by an exclamation point rather than a period: 

How wonderful!
Ow! That hurt!
Exclamations are also used to express greetings or congratulations:
Well done, guys!




Grammar and usage