noun plural

Arach·​ni·​da ə-ˈrak-nəd-ə How to pronounce Arachnida (audio)
: a large class of arthropods that are mostly air-breathing by means of trachea or book lungs, that include the spiders and scorpions, mites, and ticks, and that have a segmented body divided into two regions of which the anterior bears four pairs of legs but no antennae
arachnid adjective or noun

Dictionary Entries Near Arachnida

Cite this Entry

“Arachnida.” Medical Dictionary, Merriam-Webster, Accessed 26 Jan. 2023.

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Commonly Confused Words Quiz

  • vector image of a face with thought expression
  • I went to the ______ store to buy a birthday card.
Spell It

Hear a word and type it out. How many can you get right?

Solve today's spelling word game by finding as many words as you can with using just 7 letters. Longer words score more points.

Can you make 12 words with 7 letters?