Definition of diurnal in English:



  • 1Of or during the day.

    • ‘When I was first married I was practically nocturnal, and my wife was diurnal.’
    • ‘It's now 6am, which is the equivalent of 6pm for all of those conservative diurnal types.’
    • ‘I'll get maybe three, four good diurnal emissions off per day, I reckon.’
    • ‘The mercury levels now seem to have changed with diurnal temperature difference narrowing down.’
    • ‘A feature shared by many clock gene transcripts is that their abundance is subject to circadian and diurnal oscillation.’
    active during the day, non-nocturnal
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    1. 1.1Zoology (of animals) active in the daytime.
      • ‘They are diurnal herbivores, hiding in reef crevices during nighttime and browsing over reefs to feed during the day.’
      • ‘Conversely, subdominant fish were diurnal and occupied large home ranges by day but were generally not observed at night.’
      • ‘Accipitrids are diurnal birds of prey with broad wings, hooked beaks, strong legs and feet and sharp talons.’
      • ‘The male provides no direct parental care except to protect the eggs against diurnal fish predators.’
      • ‘Finally, group living often provides diurnal rodents with better predator defenses.’
    2. 1.2Botany (of flowers) open only during the day.
      • ‘Are diurnal changes of turgor and leaf growth correlated with each other?’
      • ‘Ammonium concentrations in roots and leaves undergo diurnal changes.’
      • ‘NRA showed important diurnal changes in leaves and roots tissues.’
      • ‘There are only marginal changes in phosphorylated intermediates in the diurnal time-frame or during tuber development.’
      • ‘The sample traces (a, b) are representative of the diurnal pattern of leaf extension rate for each species.’
  • 2Daily; of each day.

    ‘diurnal rhythms’
    • ‘Universal, reliable and even human-made light, completely independent of diurnal rhythm, has abolished the shamanist aspects of our calling.’
    • ‘This apparently inefficient system gives us the ability to deal with the natural variability of the diurnal rhythms of light and temperature.’
    • ‘The diurnal rhythm of cortisol secretion in the horse peaks at approximately 0600 h and is least at approximately 1800 h.’
    • ‘Moreover, while minor amino acids show marked diurnal rhythms, their contents fluctuate in a co-ordinated manner.’
    • ‘The APR of maize and Arabidopsis thaliana follows a diurnal rhythm with maximum activity during the light period.’
    • ‘The absence of a diurnal rhythm would be a significant difference between growth control in roots and dicot leaves.’
    • ‘Experiments were performed always at the same time of the day, to avoid interference with diurnal rhythms.’
    • ‘The transporters show different expression patterns in response to diurnal rhythm.’
    • ‘This impulse to explore the diurnal is shared by cinema which similarly took everyday objects and put them on exhibit as a form of ‘art’.’
    • ‘For the most part, this diurnal ritual occurs around 6: 30 a.m.’
    • ‘What I needed for recovery was a long period of rest in a comfortable setting with a familiar diurnal schedule.’
    • ‘Her diurnal ritual of hurriedly brushing her hair before the mirror expands to one of self-admiration.’
    • ‘They have their own diurnal cycles, pegged to alien time-frames.’
    • ‘Today FM, for example, operates to a finely calibrated diurnal rhythm, carefully tuned to the mood of its audience.’
    • ‘Too late for conventional diurnal rhythms; too early for genuine nocturnal ones.’
    daily, everyday, day-to-day, quotidian
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    1. 2.1Astronomy Of or resulting from the daily rotation of the earth.
      ‘diurnal aberration’
      • ‘Magnetism, in other words, caused the Earth's Copernican diurnal rotation.’
      • ‘In poetic form, Aryabhata stated that the earth's diurnal rotation on its axis produced the daily rising and setting of planets and stars.’
      • ‘Right ascension makes it easy to use the apparent diurnal rotation of the celestial sphere as a means to telling time.’
      • ‘He explained eclipses, solstices and equinoxes, announced the sphericity of the earth and its diurnal revolution on its axis.’
      • ‘What mattered was the planet's diurnal position relative to the horizon - whether it was rising in the east or culminating overhead.’


Late Middle English (as a term in astronomy): from late Latin diurnalis, from Latin diurnus ‘daily’, from dies ‘day’.