Ha (interjection)

1. Used to express various emotions, such as surprise, amusement, delight, or triumph.
2. Used as an exclamation to attract attention or to express derision.

Origin:

Late 16th century (originally a call to attract attention in hunting): imitative.

Examples:

1. Ha! I told you so!
2. Ha, ha, that's a good one!
3. Ha, I caught you!
4. Ha! I won!
5. Ha, what a beautiful day it is!