There isn't really a single perfect synonym for "common noun." However, depending on the context, you could use:

* General noun: This emphasizes the broadness of the category the noun represents.

* Generic noun: This highlights the non-specific nature of the noun.

* Concrete noun: If the common noun refers to something tangible.

* Abstract noun: If the common noun refers to something intangible.

Ultimately, the best substitute depends on the specific meaning you want to convey.