blue

adj. having a blue color; sad, depressed (slang)

n. color blue, color of the sky or sea

v. paint blue; treat with bluing (substance used to whiten clothes); waste money, spend extravagantly (Slang)

The term blue may refer to any of a number of similar colours. The sensation of blue is made by light having a spectrum dominated by energy in the wavelength range of about 440–490 nm. Blue is considered to be one of the three primary additive colours in the RGB system; blue light has the shortest wavelength range of the three additive primary colours. The English language commonly uses "blue" to refer to any colour from navy blue to cyan. The complementary colour of blue in colour science is yellow (on the HSV colour wheel), while in art the complementary colour to blue is considered to be orange (based on the Munsell colour wheel).
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This article is not about Gauss–Markov processes. In statistics, the Gauss–Markov theorem, named after Carl Friedrich Gauss and Andrey Markov, states that in a linear model in which the errors have expectation zero and are uncorrelated and have equal variances, the best linear unbiased estimators of the coefficients are the least-squares estimators. More generally, the best linear unbiased estimator of any linear combination of the coefficients is its least-squares estimator. The errors are not assumed to be normally distributed, nor are they assumed to be independent (but only uncorrelated — a weaker condition), nor are they assumed to be identically distributed (but only having zero mean and equal variances).
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Noun
1. the color of the clear sky in the daytime; "he had eyes of bright blue"
(synonym) blueness
(hypernym) chromatic color, chromatic colour, spectral color, spectral colour
(hyponym) azure, cerulean, sapphire, lazuline, sky-blue
2. blue clothing; "she was wearing blue"
(hypernym) clothing, article of clothing, vesture, wear
3. any organization or party whose uniforms or badges are blue; "the Union army was a vast blue"
(hypernym) organization, organisation
(hyponym) Union Army
4. the sky as viewed during daylight; "he shot an arrow into the blue"
(synonym) blue sky, blue air, wild blue yonder
(hypernym) sky
5. used to whiten laundry or hair or give it a bluish tinge
(synonym) bluing, blueing
(hypernym) dye, dyestuff
6. the sodium salt of amobarbital that is used as a barbiturate; used as a sedative and a hypnotic
(synonym) amobarbital sodium, blue angel, blue devil, Amytal
(hypernym) amobarbital
7. any of numerous small chiefly blue butterflies of the family Lycaenidae
(hypernym) lycaenid, lycaenid butterfly
(member-holonym) Lycaena, genus Lycaena
Verb
1. turn blue
(hypernym) discolor, discolour, colour, color
(derivation) blueness
Adjective
1. having a color similar to that of a clear unclouded sky; "October's bright blue weather"- Helen Hunt Jackson; "a blue flame"; "blue haze of tobacco smoke"
(synonym) bluish, blueish, light-blue, dark-blue, blue-black
(similar) chromatic
2. used to signify the Union forces in the Civil War (who wore blue uniforms); "a ragged blue line"
(similar) northern
3. low in spirits; "lonely and blue in a strange city"; "depressed by the loss of his job"; "a dispirited and resigned expression on her face"; "downcast after his defeat"; "feeling discouraged and downhearted"
(synonym) depressed, dispirited, down(p), downcast, downhearted, down in the mouth, low, low-spirited
(similar) dejected
4. characterized by profanity or cursing; "foul-mouthed and blasphemous"; "blue language"; "profane words"
(synonym) blasphemous, profane
(similar) dirty
5. suggestive of sexual impropriety; "a blue movie"; "blue jokes"; "he skips asterisks and gives you the gamy details"; "a juicy scandal"; "a naughty wink"; "naughty words"; "racy anecdotes"; "a risque story"; "spicy gossip"
(synonym) gamy, gamey, juicy, naughty, racy, risque, spicy
(similar) sexy
6. belonging to or characteristic of the nobility or aristocracy; "an aristocratic family"; "aristocratic Bostonians"; "aristocratic government"; "a blue family"; "blue blood"; "the blue-blooded aristocracy"; "of gentle blood"; "patrician landholders of the American South"; "aristocratic bearing"; "aristocratic features"; "patrician tastes"
(synonym) aristocratic, aristocratical, blue-blooded, gentle, patrician
(similar) noble
7. morally rigorous and strict; "blue laws"; "the puritan work ethic"; "puritanic distaste for alcohol"; "she was anything but puritanical in her behavior"
(synonym) blue(a), puritan, puritanic, puritanical
(similar) nonindulgent
8. causing dejection; "a blue day"; "the dark days of the war"; "a week of rainy depressing weather"; "a disconsolate winter landscape"; "the first dismal dispiriting days of November"; "a dark gloomy day"; "grim rainy weather"
(synonym) dark, depressing, disconsolate, dismal, dispiriting, gloomy, grim
(similar) cheerless, uncheerful

(v. t.)
To make blue; to dye of a blue color; to make blue by heating, as metals, etc.
  

(superl.)
Suited to produce low spirits; gloomy in prospect; as, thongs looked blue.
  

(superl.)
Severe or over strict in morals; gloom; as, blue and sour religionists; suiting one who is over strict in morals; inculcating an impracticable, severe, or gloomy mortality; as, blue laws.
  

(superl.)
Pale, without redness or glare, -- said of a flame; hence, of the color of burning brimstone, betokening the presence of ghosts or devils; as, the candle burns blue; the air was blue with oaths.
  

(superl.)
Low in spirits; melancholy; as, to feel blue.
  

(superl.)
Literary; -- applied to women; -- an abbreviation of bluestocking.
  

(superl.)
Having the color of the clear sky, or a hue resembling it, whether lighter or darker; as, the deep, blue sea; as blue as a sapphire; blue violets.
  

(pl.)
Low spirits; a fit of despondency; melancholy.
  

(n.)
One of the seven colors into which the rays of light divide themselves, when refracted through a glass prism; the color of the clear sky, or a color resembling that, whether lighter or darker; a pigment having such color. Sometimes, poetically, the sky.
  

(n.)
A pedantic woman; a bluestocking.
  

A language proposed by Softech to meet the DoD Ironman requirements which led to Ada. ["On the BLUE Language Submitted to the DoD", E.W. Dijkstra, SIGPLAN Notices 13(10):10-15 (Oct 1978)].