**to a first approximation**: adj. 1. [techspeak] When one is doing certain numerical computations, an
approximate solution may be computed by any of several heuristic methods,
then refined to a final value. By using the starting point of a first
approximation of the answer, one can write an algorithm that converges more
quickly to the correct result.

2. In jargon, a preface to any comment that indicates that the
comment is only approximately true. The remark “To a first
approximation, I feel good” might indicate that deeper questioning
would reveal that not all is perfect (e.g., a nagging cough still remains
after an illness).