What is the difference between nominal size and actual size in lumber?

Nominal size refers to the dimensions assigned to lumber before it has gone through the processes of drying and planing, which give it its final, usable dimensions. For example, a piece of lumber labeled as 2x4 inches is actually measured before it is dried and surfaced, which causes it to shrink. The actual size of this lumber, once it has been processed, will measure about 1.5x3.5 inches.

This distinction is crucial for carpenters and builders, as they need to understand the size of lumber when estimating dimensions for building structures and woodworking projects. Proper understanding of these terms helps in ensuring that the correct materials are selected for any given task, avoiding mistakes related to size discrepancies. The other options may suggest different interpretations, but they do not accurately represent the industry-standard definitions of nominal and actual sizes of lumber.