What kitchen equipment is typically used for grinding spices or herbs?

The mortar and pestle is specifically designed for grinding spices and herbs, making it the ideal choice among the options provided. This traditional tool allows for precise control over the grinding process, enabling the user to achieve the desired texture and flavor extraction. The rough surfaces of the mortar and pestle facilitate the crushing and grinding, releasing the essential oils and enhancing the flavors of the spices and herbs.

While a food processor and a blender can also be used for chopping or pureeing, they might not provide the same degree of control or preserve the integrity of the herb or spice as effectively as a mortar and pestle. A knife is not suitable for grinding; instead, it is used primarily for chopping or slicing. Therefore, the mortar and pestle stands out as the correct answer due to its specialized and effective design for grinding tasks in the kitchen.