Exclamative

a type of sentence structure used to express strong emotion.

Also known as exclamatory sentences.

Compare:
 * Declarative
 * Interrogative
 * Imperative

Structure
Exclamatory sentences often begin with what or how:
 * What an amazing story that is!
 * How beautiful the music was!

Exclamatory structures can also be reduced (elliptical):
 * What a shock!

Crystal, David. Rediscover Grammar, page 54.

Bruntt, Karen and Bryanne, Ulla. Handbook for Grammar Detectives, page 113.