perhaps it's the domain people refer to? For example: A chair that I make is unique, there is not another exactly like it. A chair that I make is unique, the

perhaps it's the domain people refer to? For example: A chair that I make is unique, there is not another exactly like it. A chair that I make is unique, there is only one in the world made by me. In this case, the chair is unique in a very specific way. However, the Babbage engine is unique in more ways. First mechanical computer of a certain complexity. Only mechanical computer with so much funding from the government. Build quality, ability etc...