Definition of Arachnida in English:


plural noun

  • A class of chelicerate arthropods that includes spiders, scorpions, mites, and ticks. They have become adapted for a terrestrial life and possess both lungs and tracheae, and many have silk or poison glands.

    • ‘Ticks belong to the class Arachnida, which counts mites, spiders and scorpions among its members.’
    • ‘The Arachnida are notorious for the venomous organisms that form part of this class.’
    • ‘However, they were not true spiders, nor necessarily ancestral to them, but represented independent offshoots of the Arachnida.’
    • ‘The Arachnida include the terrestrial chelicerates that everyone is familiar with, and that nearly everyone would rather not be too familiar with: spiders, ticks and mites, and scorpions (Scorpiones).’
    • ‘The study of the Southern African baboon spiders form part of the South African National Survey of Arachnida.’


Modern Latin (plural), from Greek arakhnē ‘spider’.