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For All Practical Purposes (FAPP) is a pragmatic approach towards the problem of incompleteness of every scientific theory and the usage of asymptotical approximations.
Usually, when a physicist makes an approximation - which can't be justified on rigorous grounds - he tends to justify it by saying that the results obtained are good for all practical purposes (FAPP), meaning that they agree with our experience and approximation errors cannot be detected in practical measurements (for instance, if the error is smaller than the measurement resolution).
FAPP theories are incomplete or lackly-based theories that nevertheless have very high agreement with experiments and tend to be very useful for all practical purposes.
Famous quotes containing the words practical and/or purposes:
“When ... I comprehended that poetry had no provision in it for ultimate practical attainment of the rightness of work that is truth, but led on ever only to a temporizing less- than-truth ... I stopped.”
—Laura (Riding)
“O, I am smitten with a hatchet’s jaw;
And that in deed and not in word alone.
chorus: I thought I heard a sound within the house
Unlike the voice of one that jumps for joy.
He splits my skull, not in a friendly way,
Once more: he purposes to kill me dead”
—A.E. (Alfred Edward)