nocturnal

American  

[nok-tur-nl] / nɒkˈtɜr nl /

adjective

1. of or relating to the night (opposed to diurnal).

2. done, occurring, or coming at night.

   nocturnal visit.

   Synonyms:

   nighttime

3. active at night (opposed to diurnal).

   nocturnal animals.

4. opening by night and closing by day, as certain flowers (opposed to diurnal).

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noun

1. Archaic. an astrolabe for telling time at night or for determining latitude by the position of certain stars in reference to Polaris.

nocturnal British  

/ nɒkˈtɜːnəl /

adjective

1. of, used during, occurring in, or relating to the night

2. (of animals) active at night

3. (of plants) having flowers that open at night and close by day

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nocturnal Scientific  

/ nŏk-tûr′nəl /

1. Occurring at night.

2. Most active at night. Many animals, such as owls and bats, are nocturnal.

3. Having flowers that open during the night and close at daylight. Nocturnal plants are often pollinated by moths.

4. Compare diurnal

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Other Word Forms

• nocturnality
  noun
• nonnocturnal
  adjective
• seminocturnal
  adjective
• unnocturnal
  adjective
• nocturnally
  adverb
• nonnocturnally
  adverb
• unnocturnally
  adverb

Etymology

Origin of nocturnal

From the Late Latin word nocturnālis, dating back to 1475–85. See nocturn, -al ¹

Explanation

If something is nocturnal, it belongs to or is active at night. That includes vampires, owls that like to hunt by moonlight, and that roommate who stays up playing video games until the wee hours of the morning. The adjective nocturnal comes from the Late Latin nocturnalis, which means “belonging to the night." You've probably heard of nocturnal animals, like bats and fireflies, who sleep during the day and come out to play when the sun goes down. The opposite of nocturnal is diurnal, meaning active during the daytime — but you probably won't be using that word much unless you're a zoologist.

Example Sentences

It'll take you a few days to fully adapt, but after that you'll be almost nocturnal and will manage to take in the England game and all the other late-night fixtures.

From BBC • Jul. 5, 2026

Mountain lions are primarily nocturnal, which means they are usually active when people are not.

From Science Daily • Jun. 28, 2026

Researchers believe the nocturnal predator developed the unique hunting method to make meals of aggressive ants which are notoriously dangerous - and unusual - prey for arachnids.

From BBC • Jun. 23, 2026

The Black Badge specification features a dark-anodized grille and hood figurine in the place of chrome brightwork—younger, fresher, more nocturnal, but also nicely understated, which I like.

From The Wall Street Journal • Apr. 4, 2026

The girls weren’t always easy to manage, and since Sarai was nocturnal by necessity, it mostly fell to Feral to see that they did their chores and obeyed The Rule.

From "Strange the Dreamer" by Laini Taylor

Related Words

• nightly
• nighttime