Here's why:

* Taxonomy is the science of classifying organisms into groups based on their shared characteristics. A crucial part of this is nomenclature, which is the formal system of naming organisms.

* Nomenclature itself is the process of giving names to things, so it's a more specific term related to the naming part of taxonomy.

So, while "nomenclature" focuses solely on the naming process, "taxonomy" encompasses the entire classification system, including naming.