【Imperfection】 , 【deficiency】 ,  【shortcoming】 ,  【fault】  mean a failure in persons or in things to reach a standard of excellence or perfection.

【Imperfection】  is the most general of these words; it usually does not imply a great departure from perfection and is usually replaceable by a more specific term (as flaw, blemish, defect, failing, frailty, or foible ) which emphasizes its slightness rather than its enormity.

【Deficiency】  carries a clear implication of lack or of inadequacy, whether moral or mental, physical or spiritual; it applies particularly to persons, but it may refer also to an inadequacy in things which affects the persons involved. Unlike  【imperfection】 , it often implies a great departure from a standard of perfection or sufficiency.

【Shortcoming】 implies 【deficiency】 but is seldom used in quite the same sense. Often it implies a standard of perfection or of excellence which is hard to reach and then suggests not so much the degree of 【imperfection】 or 【deficiency】 as (the doer’s) sense of failure to reach the standard or (the critic’s or judge’s) unwillingness to use a harsher or more direct term.

【Fault】  (see also  【FAULT】  ) is more direct and clear-cut in statement than any of the others; it usually implies personal culpability for the failing in a person or direct blameworthiness for the 【shortcoming】 or defect in a thing; often, also, it permits description of the failing or defect.