Do we have proper terminology in both Sinhala and Tamil Languages?
What are the best choices available? We can't say: සෙකියුල ශ්රි ලංකා ! Need sinhala and tamil words. Check wikipedia definitions and think about how Indians defined this in hindi and other indian sub continent languages. Must clearly address strict separation, not half way separation of state. Meaning of 'non-aligned', non-religious, irreligious state are ideas to think about, but it appears direct anti-theistic words may not be needed as long as it clearly defines the separation or state and religion.
In Sinhala: අනාගමික, නිආගමික, I don't think these words do good justice, we need a more sophisticated word of its own class.