FWIT, I’ve published a [taxonomy of inconsistencies][1] to aid in user performance analysis, but I suspect it isn’t widely known.

Inconsistency within different parts of the same product are **internal**, while inconsistency between a product and some other reference (e.g., a standard, a legacy product, or a metaphor) are **external**.

A **contradiction** is when the same thing has two different usages. An **irregularity** is when two different things have the same usage.

The “things” above can be symbols, codes, unit use, formats, terms (like your case), abbreviations, and layout (That makes the mnemonic acronym SCUFTAL).

So what you have is an **internal terminology contradiction**… which, as you probably know, is really bad.


  [1]: http://www.uxmatters.com/mt/archives/2010/07/achieving-and-balancing-consistency-in-user-interface-design.php