What is the term for a structural member that has a nominal thickness between 2 to 4 inches?

The term "dimensional lumber" specifically refers to structural lumber that is cut to standardized widths and depths, typically ranging from 2 to 4 inches in thickness. This classification is significant in construction as it encompasses commonly used sizes for framing and supports in buildings. Dimensional lumber is well-structured for various applications, making it an essential component in the building trades. In contrast, "timber" generally refers to larger structural members, often exceeding 5 inches in thickness, while "board" typically indicates a thinner material, usually less than 2 inches thick. "Structural lumber" is a broad category that includes both dimensional lumber and timber but does not pinpoint the specific thickness range mentioned in the question. Therefore, dimensional lumber is the most accurate term for a structural member with a nominal thickness between 2 to 4 inches.