[huhtenberg]

Not sure why, but this reminds me how we had a professor that would say

  Let y(x) = a*x^4 + b*x^3 + c*x^2 + d*x + e,
  whereby e is not _necessarily_ the base of 
  natural logarithm

[cperciva]

My favourite along those lines was "let epsilon be a small number which is not necessarily greater than zero". Everybody who spent the preceding year on epsilon-delta proofs did a double-take at that.