Compounds of なんです

• なんです
  (aux) it is assuredly that ...
  can say with confidence that ...
• そうなんです
  (int) (col) yes
  that is so
• そうなんですか
  (exp) is that so?
• いったい何なんですか
  (exp) what is it exactly?
  what is it precisely
• そうなんですけどねぇ
  (exp) that may be so