All Words Glossary

Glossary of Astronomy Terms
beginning with letter D
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day Tweet Definition of day Like Definition of day on Facebook
  1. A period of 24 hours.
  2. The period from midnight to the following midnight. There are 7 days in a week: Sunday, Monday, Tuesday, Wednesday, Thursday, Friday, and Saturday.
  3. Rotational period of a planet (especially earth).
  4. The part of a day period which one spends at one"s job, school, etc.
    • I worked two days last week.
      1. Part of a day period between sunrise and sunset where one enjoys daylight, daytime.
    • and night. (rfex, also for the last)
daystar Tweet Definition of daystar Like Definition of daystar on Facebook
  1. The morning star; the planet Venus.
    • 1809, w:Joel Barlow, Joel Barlow, The Columbiad, book VI, l. 245
    • : Here dawn'd the of Hesperia's fame, / Here herald glory first emblazed her name;
    • 1865, Common English Version of the Bible, 2 Peter 1:19
    • : And we have more sure the prophetic word; to which ye do well that ye take heed, as to a lamp shining in a dark place, until the day dawn, and the arise in your hearts;
      1. (poetic) The Sun.
      I only go outdoors at night, away from the 's burning glare.
declination Tweet Definition of declination Like Definition of declination on Facebook
  1. At a given point, the angle between magnetic north and true north.
  2. At a given point, the angle between the line connecting this point with the geographical center of the earth and the equatorial plane.
  3. A refusal.
  4. (archaic) declension, Declension.
deferent Tweet Definition of deferent Like Definition of deferent on Facebook
  1. showing deference
Delphinus Tweet Definition of Delphinus Like Definition of Delphinus on Facebook
proper noun 
  1. (constellation) A small summer constellation of the northern sky, said to resemble a dolphin. It lies between the constellations Cygnus and Aquila.
Deneb Tweet Definition of Deneb Like Definition of Deneb on Facebook
proper noun 
  1. (star): A blue giant star in the constellation Cygnus; Alpha (α) Cygni. It forms one corner of the Summer Triangle. Deneb is one of the brightest stars in the night sky, and one of the most luminous stars known.
depression Tweet Definition of depression Like Definition of depression on Facebook
  1. (context, geography) an area that is lower in topography than its surroundings
  2. (context, psychology) in psychotherapy and psychiatry, a state of mind producing serious, long-term lowering of enjoyment of life or inability to visualize a happy future
  3. (context, psychology) in psychotherapy and psychiatry, a period of unhappiness or low morale which lasts longer than several weeks and may include ideation of self-inflicted injury or suicide
  4. (context, meteorology) an area of lowered air pressure that generally brings moist weather, sometimes promoting hurricanes and tornadoes
  5. (context, economics) a period of major economic contraction
The Great Depression (US history)
  1. (context, biology, physiology) a lowering, in particular a reduction in a particular biological variable or the function of an organ, in contrast to elevation
digit Tweet Definition of digit Like Definition of digit on Facebook
  1. A finger or toe.
  2. (arithmetic) A numeral that can be combined with others to write larger numbers, and that cannot itself be split into other numerals.
The digits of the decimal number system are 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9, and those in the hexadecimal number system are those in the decimal system along with A, B, C, D, E and F.
The number 2307 has four digits: the thousands digit is 2; the hundreds digit is 3; the tens digit is 0; and the units digit is 7.
  1. (context, slang, UK, in plural) One's phone number.
That girl likes me — she gave me her digits.
Dog Star Tweet Definition of Dog Star Like Definition of Dog Star on Facebook
proper noun 
  1. (star) A bluish-white star in the constellation Canis Major; Alpha (α) Canis Majoris. A vertex of the Winter Triangle and the brightest star in the night sky. It is actually a binary star with a white dwarf companion star.
double star Tweet Definition of double star Like Definition of double star on Facebook
  1. (astronomy) Two stars which form a stellar system, such that they orbit the point of equilibrium of their gravitational fields; a binary star.
  2. (astronomy) Two stars that appear to be one when seen with the naked eye, either because they orbit one another (binary stars) or happen to be in the same line of sight even though they are separated by a great distance (optical binary star, optical binaries).
draconic month Tweet Definition of draconic month Like Definition of draconic month on Facebook
  1. A period of time between two consecutive passages of the Moon through the same orbital node. The draconic month is shorter than sidereal month, due to precession of the Moon's orbit. It equals approximately 27 days 5 hours 5 minutes 35.8 seconds. It is also called draconitic month.
dwarf Tweet Definition of dwarf Like Definition of dwarf on Facebook
noun (pl2=dwarves)
  1. A person with short stature, often one whose limbs are disproportionately small in relation to the body as compared with normal adults, usually as the result of a genetic condition.
  2. An animal, plant or other thing much smaller than the usual of its sort.
  3. A creature from folklore, usually depicted as having mystical powers and being skilled at crafts such as woodwork and metalworking. Especially often found in Scandinavian folklore. Sometimes pluralized dwarves, especially in modern fantasy literature.
  4. (star) A star of relatively small size.
  1. (transitive) To make (to appear) much smaller; to render puny or tiny
The newly-built skyscraper dwarfs the older buildings that make up the rest of downtown.
Bach dwarfs all other composers.
  1. miniature

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