from The American Heritage® Dictionary of the English Language, 5th Edition.

  • adjective Relating to or occurring in a 24-hour period; daily.
  • adjective Occurring or active during the daytime rather than at night.
  • adjective Botany Opening during daylight hours and closing at night.
  • noun A book containing all the offices for the daily canonical hours of prayer except matins.
  • noun A diary or journal.
  • noun A daily newspaper.

from The Century Dictionary.

  • Of or belonging to day; pertaining to the daytime; belonging to the period of daylight, as distinguished from the night: opposed to nocturnal: as, diurnal heat; diurnal hours; diurnal habits, as of an animal.
  • Daily; happening every day: as, a diurnal task.
  • Performed in or occupying one day; lasting but for one day; ephemeral.
  • Constituting the measure of a day, either on the earth or one of the other planets: as, the diurnal revolution of the earth, or of Mars or Jupiter.
  • Characterized by some change or peculiarity which appears and disappears with the daytime,
  • noun A day-book; a diary; a journal.
  • noun A daily newspaper.
  • noun A Roman Catholic service-book containing the offices for the daily hours of prayer.
  • noun In ornithology, a diurnal bird of prey.
  • noun In entomology, one of the Diurna.

from the GNU version of the Collaborative International Dictionary of English.

  • noun obsolete A daybook; a journal.
  • noun (R. C. Ch.) A small volume containing the daily service for the “little hours,” viz., prime, tierce, sext, nones, vespers, and compline.
  • noun (Zoöl.) A diurnal bird or insect.
  • adjective Relating to the daytime; belonging to the period of daylight, distinguished from the night; -- opposed to nocturnal
  • adjective Daily; recurring every day; performed in a day; going through its changes in a day; constituting the measure of a day
  • adjective (Bot.) Opening during the day, and closing at night; -- said of flowers or leaves.
  • adjective (Zoöl.) Active by day; -- applied especially to the eagles and hawks among raptorial birds, and to butterflies (Diurna) among insects.
  • adjective (Anat.) the aberration of light arising from the effect of the earth's rotation upon the apparent direction of motion of light.
  • adjective the arc described by the sun during the daytime or while above the horizon; hence, the arc described by the moon or a star from rising to setting.
  • adjective the apparent circle described by a celestial body in consequence of the earth's rotation.
  • adjective the motion of the earth upon its axis which is described in twenty-four hours.
  • adjective that apparent motion of the heavenly body which is due to the earth's diurnal motion.
  • adjective See under Parallax.
  • adjective the motion of the planet upon its own axis which constitutes one complete revolution.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • adjective Happening or occurring during daylight, or primarily active during that time.
  • adjective botany Said of a flower open, or releasing its perfume during daylight hours, but not at night.
  • adjective Having a daily cycle that is completed every 24 hours, usually referring to tasks, processes, tides, or sunrise to sunset.
  • adjective uncommon Done once every day; daily, quotidian.
  • adjective archaic Published daily.
  • noun A flower that opens only in the day.
  • noun Catholicism A book containing canonical offices performed during the day, hence not matins.
  • noun archaic A diary or journal.
  • noun archaic A daily news publication.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • adjective of or belonging to or active during the day
  • adjective having a daily cycle or occurring every day


from The American Heritage® Dictionary of the English Language, 4th Edition

[Middle English, from Late Latin diurnālis, from Latin diurnus, from diēs, day; see dyeu- in Indo-European roots.]

from Wiktionary, Creative Commons Attribution/Share-Alike License

From Latin diurnālis, from diēs ("day"). Cognate with journal.


  • Apparently, McLeanian logic tells us that the rotation of the earth also explains the seasons, considering how well it correlates with the short-term diurnal variation...

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  • There is also a great difference between day and night high water; the difference between them is called the diurnal tide.

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  • God then willed the revolution of the outermost sphere, known as the diurnal sphere, which caused all the other spheres to revolve with it, thereby producing changes in the hyle in accordance with the motions of the sphere.

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  • In a similar manner, what is called the diurnal variation of the barometer, which is very small compared with the variations arising from the irregular changes in the state of the atmosphere, was discovered by comparing the average height of the barometer at different hours of the day.

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  • Scientists have now observed that one of these atmospheric tides, known as diurnal wavenumber

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  • For the circle around the insertion is seen to increase, and to inflame; and I believe, undergoes a kind of diurnal paroxysm of torpor and paleness with a succeeding increase of action and colour, like a topical fever-fit.

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  • Thursday and Friday will both feature "diurnal" cloudiness, which means some morning sunshine followed by increasing clouds and mostly cloudy afternoons.

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  • My search revealed the words "diurnal," "dewlap," "osmoregulation," and "Guatemala," all technical terms that relate to the iguana in some way, shape or form.

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  • (* This difference in the heights of consecutive tides is termed the diurnal inequality.

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  • * (* This difference in the heights of consecutive tides is termed the diurnal inequality.

    Captain Cook's Journal During the First Voyage Round the World


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  • Poor Wordnik, now in condition infernal.
    I pray will resume its mission fraternal;
    While words may be wished
    In puns and in lists,
    Still mostly I miss the emission diurnal.

    December 10, 2014