Noun

(uncountable) Inadequacy or incompleteness.

* {{quote-book, year=1963, author=(Margery Allingham), title=(The China Governess)

, chapter=17 citation , passage=The face which emerged was not reassuring. […]. He was not a mongol but there was a deficiency of a sort there, and it was not made more pretty by a latter-day hair cut which involved eccentrically long elf-locks and oiled black curls.}}

(countable) An insufficiency, especially of something essential to health.

* {{quote-magazine, date=2013-08-31, volume=408, issue=8851, magazine=(The Economist)

, title= Promotion and self-promotion , passage=One of academia’s deficiencies is that, though its lecture halls and graduate schools are replete with women, its higher echelons are not. Often, this is seen as a phenomenon specific to the sciences. … In fact, the disparity applies to the whole grove. Another report from 2006, by the American Association of University Professors, found the same ratio in the faculties of arts, humanities and social science, too.}}

(geometry) The amount by which the number of double points on a curve is short of the maximum for curves of the same degree.

(geometry) The codimension of a linear system in the corresponding complete linear system.

Noun

(en noun)

(obsolete) A defect or failing; moral or spiritual degeneracy.

*

, title=(The Celebrity), chapter=1 , passage=In the old days, to my commonplace and unobserving mind, he gave no evidences of genius whatsoever. He never read me any of his manuscripts, […], and therefore my lack of detection of his promise may in some degree be pardoned.}}

A deficiency or need (of something desirable or necessary); an absence, want.

* Shakespeare

Let his lack of years be no impediment.

* 1994 , (Green Day),

I went to a shrink, to analyze my dreams. He said it's lack of sex that's bringing me down.''

* {{quote-news, year=2012, date=September 7, author=Phil McNulty, work=BBC Sport

, title= Moldova 0-5 England , passage=If Moldova harboured even the slightest hopes of pulling off a comeback that would have bordered on miraculous given their lack of quality, they were snuffed out 13 minutes before the break when Oxlade-Chamberlain picked his way through midfield before releasing Defoe for a finish that should have been dealt with more convincingly by Namasco at his near post.}}