The phrase "half a cup" refers to a unit of measurement used in cooking and baking, which indicates half of a standard measuring cup. A measuring cup is typically a small container with graduated marks on its sides that allows for accurate measurements of liquids or dry ingredients. When the instruction calls for "half a cup," it means you should use exactly half of the volume indicated by one full measure, which is usually 8 tablespoons (1/4 cup) in the US system and 12 metric tablespoons (1/4 liter) in the international system.