These words indicate a lack in something that prevents it from being complete, wholly effective, or desirable. Flaw is the most general of these words, suggesting the existence or presence of something that spoils an otherwise sound entity: a flaw in his ingenious theory; an admirable character cursed by the tragic flaw of pride. While flaw suggests something that detracts from completeness, effectiveness or perfection, fault points to something that impairs excellence. A flaw can refer to something missing: The flaw in the weapon was its inability to fire rapidly. Fault usually refers to something present and to something inherent in the nature of a thing rather than external to it; flaw can refer to the superficial as well as to the profound.

• The length of her white gloves was the only flaw in her appearance; a central flaw in his argument that invalidated his entire position; a flaw (or fault ) in the marble near the base of the statue; Snobbishness was his main fault .

In connection with character, flaw is somewhat more elegant and dramatic than the more prosaic fault .

While flaw may or may not indicate something easily removed or overcome, defect often suggests a flaw so serious as to completely prevent functioning: a defect in the fuel lines that prevented the missile from blasting off. Since it is now often used of machines, its application to human personality sometimes indicates a judgmental or simplistic view of human nature, suggesting easily traceable explanations for malfunction: probing for the defect that had made him resort to violence. In other contexts defect may refer to an error or the lack of something needed for completion.

• A defect in judgement led to the accident; The defect in the microphone caused a humming sound.

Mar and blemish refer especially to marks or qualities that disfigure or make imperfect. Blemish applies particularly to defects of the skin: a facial blemish . Mar is almost obsolete as a noun, but when used may refer to any slight defect ; a mar in the finish of a vase. Figurative use of blemish is quite common; the first blemish on an otherwise spotless record.

Imperfection is closer to flaw than to defect in that it stresses malfunction less than incompleteness or lack of order: a slight imperfection in an otherwise beautiful design. Whereas flaw , however, points to a blemish that is self-evident, imperfection points more often to a lack that may be a matter of opinion. Like defect , the word also implies a pre-established canon by which to judge something: stylistic advances in his art that were regarded as imperfections by his contemporaries. And as defect relates to function, imperfection relates to form, drawing the former towards a scientific context, the latter to an artistic one. With imperfection , however, the judgement remains relative since no completely perfect thing exists.

Failing , shortcoming and foible are the mildest of these words, suggesting a specific lapse in an otherwise sound entity. All three words most commonly related to personality, describing a characteristic way of behaving that is not desirable but does not vitiate goodness or overall effectiveness. Foible is perhaps the mildest of the three, suggesting a slight but ingrained eccentricity that may be easily recognized by others and allowed for without causing great difficulties. A foible may, in fact, be almost harmless and even endearing: a love that was strengthened rather than weakened by their acceptance of each other’s foibles . Failing may suggest a more severe shortcoming that has more serious consequences: a lack of compassion that can be an insurmountable failing in either husband or wife. Sometimes the special point of the word is to indicate well-intentioned effort that does not succeed: the lack of convincing evidence that is the book’s main failing . Shortcoming , like failing , may refer to failures or deficiencies in things as well as people, and in this sense compares with one sense of flaw : The weapon’s chief shortcoming (or flaw ) was its inability to fire rapidly. When applied to personality or character, it is milder than either flaw or fault , and is close to failing in meaning.

• We all have our shortcomings ?that man dotes on his wife, this one flirts with other women, a third flies into jealous rages at the drop of a hat.