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

The small nocturnal arachnid has been nicknamed the ballista spider after the ancient Roman siege weapon that launched bolts and stones using stored tension.

From Science Daily • Jun. 26, 2026

Highland Council said tackling light pollution could bring other benefits such as a cut in energy use, better protection for nocturnal wildlife - and even help people get a better night's sleep.

From BBC • May 28, 2026

Gone are the gritty warehouse districts, the nocturnal desolation of downtown and the shabby chic of South Beach.

From The Wall Street Journal • May 15, 2026

Residents of Southern California who see a mysterious streak in the nocturnal sky can chalk it up to another SpaceX launch.

From Los Angeles Times • Mar. 16, 2026

He knew nothing of the boy’s fear of ghosts and other nocturnal terrors.

From "Inkheart" by Cornelia Funke

Related Words

• nightly
• nighttime