Source : Webster's Revised Unabridged Dictionary (1913)

   {Anniversary day}. See {Anniversary}, n.

   {Astronomical day}, a period equal to the mean solar day, but
      beginning at noon instead of at midnight, its twenty-four
      hours being numbered from 1 to 24; also, the sidereal day,
      as that most used by astronomers.

   {Born days}. See under {Born}.

   {Canicular days}. See {Dog day}.

   {Civil day}, the mean solar day, used in the ordinary
      reckoning of time, and among most modern nations beginning
      at mean midnight; its hours are usually numbered in two
      series, each from 1 to 12. This is the period recognized
      by courts as constituting a day. The Babylonians and
      Hindoos began their day at sunrise, the Athenians and Jews
      at sunset, the ancient Egyptians and Romans at midnight.
      

   {Day blindness}. (Med.) See {Nyctalopia}.

   {Day by day}, or {Day after day}, daily; every day;
      continually; without intermission of a day. See under
      {By}. ``Day by day we magnify thee.'' --Book of Common
      Prayer.

   {Days in bank} (Eng. Law), certain stated days for the return
      of writs and the appearance of parties; -- so called
      because originally peculiar to the Court of Common Bench,
      or Bench (bank) as it was formerly termed. --Burrill.

   {Day in court}, a day for the appearance of parties in a
      suit.

   {Days of devotion} (R. C. Ch.), certain festivals on which
      devotion leads the faithful to attend mass. --Shipley.

   {Days of grace}. See {Grace}.

   {Days of obligation} (R. C. Ch.), festival days when it is
      obligatory on the faithful to attend Mass. --Shipley.

   {Day owl}, (Zo["o]l.), an owl that flies by day. See {Hawk
      owl}.

   {Day rule} (Eng. Law), an order of court (now abolished)
      allowing a prisoner, under certain circumstances, to go
      beyond the prison limits for a single day.

   {Day school}, one which the pupils attend only in daytime, in
      distinction from a boarding school.

   {Day sight}. (Med.) See {Hemeralopia}.

   {Day's work} (Naut.), the account or reckoning of a ship's
      course for twenty-four hours, from noon to noon.

   {From day to day}, as time passes; in the course of time; as,
      he improves from day to day.

   {Jewish day}, the time between sunset and sunset.

   {Mean solar day} (Astron.), the mean or average of all the
      apparent solar days of the year.

   {One day}, {One of these days}, at an uncertain time, usually
      of the future, rarely of the past; sooner or later.
      ``Well, niece, I hope to see you one day fitted with a
      husband.'' --Shak.

   {Only from day to day}, without certainty of continuance;
      temporarily. --Bacon.

   {Sidereal day}, the interval between two successive transits
      of the first point of Aries over the same meridian. The
      Sidereal day is 23 h. 56 m. 4.09 s. of mean solar time.

   {To win the day}, to gain the victory, to be successful. --S.
      Butler.

   {Week day}, any day of the week except Sunday; a working day.
      

   {Working day}.
      (a) A day when work may be legally done, in distinction
          from Sundays and legal holidays.
      (b) The number of hours, determined by law or custom,
          during which a workman, hired at a stated price per
          day, must work to be entitled to a day's pay.

Source : WordNet®

sidereal day
     n : the time for one complete rotation of the earth relative to
         a particular star, about 4 minutes shorter than a mean
         solar day [syn: {day}]