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.