arachnid

noun

arach·​nid ə-ˈrak-nəd 

-ˌnid

: any of a class (Arachnida) of arthropods comprising chiefly terrestrial invertebrates, including the spiders, scorpions, mites, and ticks, and having a segmented body divided into two regions of which the anterior bears four pairs of legs but no antennae

arachnid adjective

Did you know?

The term arachnid refers to a class of animals that includes spiders, scorpions, mites, and ticks. Most arachnids have a segmented body divided into two regions, with the front part bearing four pairs of legs, but no antennae. They have a hard external skeleton and range in size from the mite, which is 0.003-in (0.08-mm) long, to the 8-in (21-cm) black scorpion of Africa. As arachnids grow, they molt, or shed their skin, several times. Arachnids are primarily carnivorous, but most are unable to digest food internally, instead they inject their prey with digestive fluids, then suck the liquefied remains. Arachnids are found worldwide in nearly every habitat. Some mites and ticks are parasitic and can carry diseases. Venomous spiders and scorpions also may pose a danger to humans, but most arachnids are harmless and prey only on insects.

Examples of arachnid in a Sentence

Spiders, scorpions, mites, and ticks are arachnids.

Recent Examples on the Web

During the field trips, scientists also discovered a new species of spider-killing fungus, which spreads spores through the arachnid before killing it. — CBS News, 19 June 2026

That great size would have also posed a problem as its food sources on land were all tiny creatures such as mites and other much smaller arachnids. — Shraddha Chakradhar, CNN Money, 10 June 2026

These arachnids hatch from eggs incubated in moist woodchuck feces, then affix themselves to the nearest dupe naïve enough to leave the city. — Jay Ruttenberg, New Yorker, 8 June 2026

The spider is easily mixed up with two native North Carolinian arachnids, meaning many people misidentify native spiders as Jorō. — Eva Flowe june 4, Charlotte Observer, 4 June 2026

Word History

First Known Use

1826, in the meaning defined above

Kids Definition

arachnid

noun

arach·​nid ə-ˈrak-nəd 

-ˌnid

: any of a class of arthropods including the spiders, scorpions, mites, and ticks and having a segmented body divided into two regions of which the front part bears four pairs of legs but no antennae

arachnid adjective