Interjections are words or phrases that express strong emotion, often in a sudden or unexpected way. They stand alone and are not grammatically connected to the rest of the sentence.
Here's why "aha" fits the definition of an interjection:
* Expresses emotion: "Aha" conveys a sense of realization, understanding, or surprise.
* Sudden and unexpected: It's often used to mark a sudden insight or discovery.
* Standalone: "Aha" can appear alone or at the beginning of a sentence, without being part of the grammatical structure.
Example:
"I finally figured out the answer! Aha! It was so obvious all along."