Ethnicity and Rwanda

Ethnicity is a problematic concept when considering Rwanda. What is ethnicity? Here we have the root:
ethnic
Of or relating to a sizable group of people sharing a common and distinctive racial, national, religious, linguistic, or cultural heritage.
Being a member of a particular ethnic group, especially belonging to a national group by heritage or culture but residing outside its national boundaries: ethnic Hungarians living in northern Serbia.

(taken from Dictionary.com)
How does the conceptual framework implied by "ethnic" apply to a discussion of the internal dynamics of Rwanda? As defined above the only ethnicity in Rwanda is that of Rwandan. Granted, there are distinctions to be made aplenty. However, the word "ethnicity" just is not descriptive in the Rwandan case. Moreover, the word interferes with the attempt to understand Rwandan history and culture. The use of a word to describe a situation on which it has no baring instantly inserts an external paradigm that distorts further discourse. Discussion of inter and intra group dynamics in Rwanda has suffered greatly from the insertion of the ethnic paradigm. Unfortunately the ethnic paradigm is a self-fulfilling prophesy. Call two groups who share the same culture, religion, language and geographical location separate ethnicities long enough--say the entire 20th century--and eventually that discourse is actually to some degree descriptive of the situation on the ground.