Step 1: Define Key Terms.
- Marginal Product (MP): The extra output from one additional unit of input, with other inputs held constant.
- Average Product (AP): Output divided by the input quantity.
- Total Product (TP): The cumulative output produced by all inputs.
- Returns to Scale: How output changes in proportion to a proportional change in all inputs.
Step 2: Match Definition.
The provided definition precisely describes Marginal Product.
Final Answer: \[\boxed{\text{Marginal Product}}\]