What are the nominal dimensions for a 1x2 stick of lumber, a 2x4 stick of lumber and a standard sheet of plywood?

3/4 x 1 1/2 inches (19 x 38 mm) is the actual size for 1x2 stick of lumber,

1 1/2 x 3 1/2 inches (38 x 89 mm) is the actually size for a 2x4 stick of lumber,

Plywood is usually sold in 4 x 8-foot sheets. The most common nominal thicknesses of plywood are 1/2 inch and 3/4 inch, but once again the actual sizes are slightly different. A sheet of 1/2-inch plywood is really 15/32 inch thick, while a 3/4-inch sheet is 23/32 inch thick.

Hopefully this answers your question, I apologize if it doesn’t :)