diurnal

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adjective di·ur·nal \dī-ˈər-n^əl\

Definition of diurnal

1a : recurring every day diurnal tasksb : having a daily cycle diurnal tides
2a : of, relating to, or occurring in the daytime the city's diurnal noisesb biology : active chiefly in the daytime diurnal animalsc botany : opening during the day and closing at night diurnal flowers

diurnally

play \-n^əl-ē\ adverb

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Examples of diurnal in a Sentence

a love as constant and certain as the diurnal tides

Recent Examples of diurnal from the Web

Overall, Anderson Valley is one of California’s cooler grape-growing areas, though the diurnal swing can be as much as 40 to 50 degrees on a summer day.

— michael dunne, sacbee.com, "Anderson Valley winemakers take a ‘Dalmatian dog’ approach to their pinot noirs," 20 June 2017
Evidence suggests that a similar extravaganza of protein creation and destruction occurs in the human liver, too, but the timing is flipped to match our largely diurnal pattern.

— natalie angier, New York Times, "The Liver: A ‘Blob’ That Runs the Body," 12 June 2017
Tarsiers evolved from a diurnal, or daytime-dwelling, ancestor, splitting from other monkeys and apes around the time the dinosaurs died out, about 64.2 to 58.4 million years ago.

— myron shekelle, National Geographic, "Tiny New 'Forest Goblins' Discovered, Look Like Yoda," 4 May 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'diurnal.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

Origin and Etymology of diurnal

Middle English, from Latin diurnalis — more at journal

NEW! Time Traveler

First Known Use: 14th century

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Other Botany Terms

annual, burgeon, chloroplast, nomenclature, succulent, sylvan, xylem

diurnal

noun di·ur·nal

Definition of diurnal

1 archaic : diary, daybook
2 : journal 1a

Examples of diurnal in a Sentence

a microfilm containing a collection of diurnals published by 19th-century American abolitionists

Origin and Etymology of diurnal

see ¹diurnal

NEW! Time Traveler

First Known Use: 1600

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DIURNAL Defined for English Language Learners

diurnal

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adjective

Definition of diurnal for English Language Learners

: active mainly during the day
: happening every day

Medical Dictionary

diurnal

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adjective di·ur·nal \dī-ˈərn-^əl\

Medical Definition of diurnal

1: having a daily cycle diurnal rhythms
2a: of, relating to, or occurring in the daytime diurnal activityb: chiefly active during the daytime diurnal mosquitoes