U

Pronunciation (US):

(GB):

IPA (US):

 Dictionary entry overview: What does U mean? 

• U (noun)
  The noun U has 3 senses:

1. a base containing nitrogen that is found in RNA (but not in DNA) and derived from pyrimidine; pairs with adenine

2. a heavy toxic silvery-white radioactive metallic element; occurs in many isotopes; used for nuclear fuels and nuclear weapons

3. the 21st letter of the Roman alphabet

  Familiarity information: U used as a noun is uncommon.

• U (adjective)
  The adjective U has 1 sense:

1. (chiefly British) of or appropriate to the upper classes especially in language use

  Familiarity information: U used as an adjective is very rare.

 Dictionary entry details 

• U (noun)

Sense 1

Meaning:

A base containing nitrogen that is found in RNA (but not in DNA) and derived from pyrimidine; pairs with adenine

Classified under:

Nouns denoting substances

Synonyms:

U; uracil

Hypernyms ("U" is a kind of...):

base; nucleotide (a phosphoric ester of a nucleoside; the basic structural unit of nucleic acids (DNA or RNA))

Holonyms ("U" is a substance of...):

ribonucleic acid; RNA ((biochemistry) a long linear polymer of nucleotides found in the nucleus but mainly in the cytoplasm of a cell where it is associated with microsomes; it transmits genetic information from DNA to the cytoplasm and controls certain chemical processes in the cell)

Sense 2

Meaning:

A heavy toxic silvery-white radioactive metallic element; occurs in many isotopes; used for nuclear fuels and nuclear weapons

Classified under:

Nouns denoting substances

Synonyms:

atomic number 92; U; uranium

Hypernyms ("U" is a kind of...):

metal; metallic element (any of several chemical elements that are usually shiny solids that conduct heat or electricity and can be formed into sheets etc.)

Hyponyms (each of the following is a kind of "U"):

uranium 235 (a uranium isotope with mass number 235; capable of sustaining chain reactions)

uranium 238 (the commonest isotope of uranium; it is not fissionable but when irradiated with neutrons it produces fissionable plutonium 239)

Holonyms ("U" is a substance of...):

pitchblende; uraninite (a mineral consisting of uranium oxide and trace amounts of radium and thorium and polonium and lead and helium; uraninite in massive form is called pitchblende which is the chief uranium ore)

Sense 3

Meaning:

The 21st letter of the Roman alphabet

Classified under:

Nouns denoting communicative processes and contents

Hypernyms ("U" is a kind of...):

alphabetic character; letter; letter of the alphabet (the conventional characters of the alphabet used to represent speech)

Holonyms ("U" is a member of...):

Latin alphabet; Roman alphabet (the alphabet evolved by the ancient Romans which serves for writing most of the languages of western Europe)

• U (adjective)

Sense 1

Meaning:

(chiefly British) of or appropriate to the upper classes especially in language use

Similar:

upper-class (occupying the highest socioeconomic position in a society)

Domain region:

Britain; Great Britain; U.K.; UK; United Kingdom; United Kingdom of Great Britain and Northern Ireland (a monarchy in northwestern Europe occupying most of the British Isles; divided into England and Scotland and Wales and Northern Ireland; 'Great Britain' is often used loosely to refer to the United Kingdom)

 Context examples 

Source: National Cancer Institute (U.S.)

(Buckminsterfullerene, The Titi Tudorancea Bulletin)

In Unicode the capital "A" is codepoint U+0041 and the lower case "a" is U+0061.

(A, The Titi Tudorancea Bulletin)

PC-SPES has been studied in the treatment of prostate cancer, but has been taken off the market in the U.S. because of safety concerns.

(PC-SPES, NCI Dictionary)

Phosphatidylinositol glycan anchor biosynthesis class U protein (435 aa, ~50 kDa) is encoded by the human PIGU gene.

(Phosphatidylinositol Glycan Anchor Biosynthesis Class U Protein, NCI Thesaurus)

Now it is a rare disease in the U.S.

(Mumps, Centers for Disease Control and Prevention)

With this introduction (which greatly affected him), Mr. Micawber placed his I.O.U. in the hands of Traddles, and said he wished him well in every relation of life.

(David Copperfield, by Charles Dickens)

The U.S. Food and Drug Administration recommends that children and women of childbearing age eat two to three weekly servings of fish low in mercury as part of a healthy diet.

(Brain benefits of aerobic exercise lost to mercury exposure, NIH)

Released to the scientific community, the map visualizes data gathered by U.S. government sensors from 1994 to 2013.

(New Map Shows Frequency of Small Asteroid Impacts, Provides Clues on Larger Asteroid Population, NASA)

The U.S. Centers for Disease Control and Prevention recommends that women of childbearing age take 400 micrograms of folic acid daily to reduce their children’s risk for neural tube defects.

(Proper maternal folate level may reduce child obesity risk, NIH)

The CDC is part of the U.S. Public Health Service of the Department of Health and Human Services (DHHS).

(CDC, NCI Dictionary)