If you're talking about the flavor**:
* Spice - This is the most general term and can refer to the ingredient itself or the flavor it imparts.
* Heat - This emphasizes the burning sensation.
* Pungency - This is a more formal term for the strong, sharp taste.
If you're talking about something spicy**:
* Spicy food
* Spicy dish
* Spicy dish
Other options:
* Chilli - This refers specifically to the ingredient.
* Pepper - This can also refer to the ingredient, but can be more general and include other spices like black pepper.
The best noun to use will depend on what you're trying to convey.