In the science of pipe an hose we deal a lot with sizes.  Almost every type of fitment comes in various sizes, a notable exception being GHT (the American designation for Garden Hose Thread), which only has one size, which is 3/4 inch. (It happens to be identical to 3/4 NST/NH, and is thus a small sub-definition of a broader specification).

This brings us to the topic of nominal versus actual size, because the 3/4 GHT isn't really 3/4 of an inch in diameter. It's actually much closer to one inch.  But 3/4 is its nominal, or trade size.  For a thorough discussion of trade size versus actual size, see the book, SIZES and MEDIUMS.